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Diagnose recent development

aceRimmer

New member
Hello,


Wondering if anyone has any thoughts on the attached pictures? The first four images are showing some yellowing on new growth for one of my four plants. Particularly at the tips, with some having very distinct regions of yellow/lighter green, as is evident in image 3. Maybe five of these leaves have begun to form small brown, rust like spots at their edges and tips (apologies for the lack of camera focus), as can be seen in image 2. This one plant has been a beast relative to the others, remaining a good 1-1.5 weeks ahead of the others in terms of relative growth (even though it has had the same feed). Some of the newer leaves of the other three plants have minor light yellow tips (see foreground leaves in image 5), but nothing to the extent of the other plant.


Throughout the grow I have also had leaves with a regular light->dark pattern, as is evident on the leaves in the center of image 5, relative to those to the left of the image, which have a uniform colour. Some of these leaves, particularly towards the base of the plant have developed brown tips and edges. As this is my first grow, I took this to be nut burn and reigned in my feeding schedule (detailed in the questionnaire below). But only recently have I realized that this 'burn' only appears on leaves with the pattern shown in image 5, and therefore might be a deficiency?


Any thoughts would be appreciated.


Thanks.



How long has this problem been going on? 2 weeks.
What system are you running? DTW.
What STRAIN are you growing? White Widow and Northern Lights.
What was the establishing technique? FemSeeds
What is the age of your plants? Approx 8 weeks from sprouting.
How long have they been in there mixture they are in now? Started in Solo cups, transplanted to 7Lt (1.8 gal) pots after 3 weeks.
How tall are the plants? 22 to 26"
What PHASE are the plants in? Veg, about to flip to flower.
What substrate/medium are you using?(Hydroton, RockWool etc.)
Canna CoCo with 25% perlite. Approx 1/2" Hydroton layer in base of pot and on its surface.
What is the Water temperature? 15-20c maybe.
What color are your roots? White? Brown? Are your roots slimy? Roots coming out drainage holes are white and not slimy.
What Nutrient's are you using?(If growing soiless) Two plants are on Canna Coco light feeding schedule, while the other two are using Head's formula.
How much of each nutrient are you using with how much water? 14L (3.7 gal) between 4 plants gives me 30% runoff. After the plants became situated I was using 2/3 Head's on two plants (~500ppm on Truncheon TDS 500 scale), and 2/3 Canna Light feeding schedule on the other two plants (~400ppm), for approx one month.

But began to see what I thought was nut burn and brought everything down to 1/2 Head's(~400ppm)/Canna(~350ppm) throughout December (though I now think what I was/am seeing is a deficiency rather than burn). I'm now feeding full strength Head's and Canna light schedule (700ppm and 550ppm respectively).
How often are you feeding? I water once every day.
How often are you giving nutrients? With every water.
What order are you mixing your nutrients? For Head's formula, Micro followed by Bloom. For Canna, it's A+B, then Rizo, then Cannazym.
What is the TDS/EC/PPM you are using As above
What is the pH of the "Tank"? pH to 5.8
How often are you testing your pH/PPM/EC/TDS? Every water.
Are you sure your calibration is correct on your equipment? I keep them calibrated.
When was your last watering? 20 hours ago.
When was your last feeding change? (ie. grow-bloom-micro-additional) Given that what I am seeing looks like it might be a deficiency, and the plant with the most severe signs is the one that's grown the most, I have been increasing my nutes from 1/2 the recommend strength to full strength over the past week. (1/2 to 2/3 to 3/4 to full).
What size bulb are you using? I'm using my own custom made LED CoB array ~300W.
What is the distance to the canopy? Distance varies, but the tallest is ~ 12" from the light. Heat density is low with 64 Cobs across an area ~1m^2 (9^2 feet), each using about ~4.5W. They are well heatsinked and unless your 1" away from the emitter you can't feel any heat. I might consider that the yellowing could be from too much light, but it is just as apparent on new growth further away from the light as it is on leaves that are the closest.
What is your RH Factor(Relative Humidity)? Humidity has been a little on the high side. Where bud sites will form it's around 70% on avg, while 80-85% at the floor of the tent. I'll have a dehumidifier set up before flowers start to develop.
What is the canopy temperature? 21-25C (70 -77f)
What is the Day/Night Temp? (Include flucutaion range) As above
What is the current Air Flow? (cfm etc.) maybe 250-300cmf. I'm using a 200mm Hyperfan at 35%, rated for max 710cmf @ 100%.
Tell us about your ventilation, intake exhaust and when its running and not running ? Exhaust is though a carbon filter, and I never turn it off. Intake is through the tents inbuilt intake holes, x2 ~200mm diameter meshed holes with circular inserts on either side to redirect light.
Is the fan blowing directly at plants? Yes, I have a 400mm (~16") wall mount reciprocating fan on High blowing from above. This also never stops.
Is your water HARD or SOFT? Very soft, truncheon reads lowest possible value. With individual ion ppm's around the single digits.
What water are you using? Reverse Osmosis (RO)? Tap? Tap. I don't bother to dechlorinate.Are you using water from a water softener? No
Has plant been recently pruned, cloned off of or pinched. I trimmed excess leaves from the base of the plants to aid in watering. This would have happened around approx 2 weeks ago. So may have something to do with it.
Have any pest chemicals been used? If so, What and When?
Are plant's infected with pest's
No. I see no sign of pests.
 

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aceRimmer

New member
Oh, I forgot to mention that a number of stems are also purple in colour, or have a purple streak to them. Though a purple stem does not always correlate with leaves showing the issues mentioned.
 

TanzanianMagic

Well-known member
Veteran
It looks like something is interfering with photosynthesis, which would point to mildew. The plants also look very crowded, which impedes airflow.

You can check by putting your head exactly above the plant and smell the top. If you smell mould instead of terpenes, it's mildew.

I would suggest to start lollypopping those plants, and spray them with something against mildew, before they go into flower.
 

DrDee

Member
Ace,
I would add that the purple stems and mild interveinal chlorosis could be Mg++ deficiency. Add in some Epsom salts at 1 tsp (5-6 grams) per gallon to see if that helps. Won't hurt anything. Magnesium is a crucial element in photosynthesis.
JD
 

Earache my eye

New member
The plants look great other than a slight deficiency which is usually caused by excess of other elements. What you’re feeding is good but if you haven’t already a good flush with plain ph’d 5.8 water will help. H3ads formula is great maybe a little low in N and Ca for some strains but it’s a nice solid formula. In coco K can become problematic and lock out Ca, N, Mg etc and some micros. Canna at 2.5ml per litre works great but lacks in K for flower so you need to add some with a little Mg too. With h3ads formula I’d add a little more micro and a bit less bloom, (higher N, Ca and micros). Purple stems with the issues you’re experiencing now in my experience usually point to N being deficient. A good solid flushing and then left to dry, (miss a watering) then feed will usually correct what you’re seeing. EC of around 1.2 allows for good calcium and Boron uptake which enables the plant to transpire and feed unimpeded lessening salt buildup. Get on top of that now before flip and don’t be scared to flush even once a week. They look great man.
 

TanzanianMagic

Well-known member
Veteran
I'm sorry however the plants don't look great. They look like they're about to be hit by a huge mildew outbreak.

Maybe there's some mag deficiency going on too - not surprising considering the soft water and the near flowering/pre-flowering state the plant is in - and epsom salt would be great because of the mg and the sulfur. Also, the room temp might be a little high, because the temperature is always warmer under the lights. Keep the room closer to 18 Celcius, and the temp of the top leaves is going to be about 25 Celcius, which is perfect.

However, that's not going to solve the problem.

Which is lack of air flow. And because the plant isn't in flowering yet, it can still be sprayed with neem oil, baking soda, bacilis subtilis and whatever is handy to defeat mildew.
 

Lester Beans

Frequent Flyer
Veteran
Raise your pH to 6.1. 5.8 is a little low for coco. Looks like the low pH is causing lockout.

Also if the hydroton in the bottom of the pots wasn't washed it could be altering your pH.
 

TanzanianMagic

Well-known member
Veteran
I have to say though, that low pH would cause lockout of mobile nutrients NPK, Mg. The damage would be from the bottom of the plant up.

The damage here is heaviest at the top of the plant - new growth, which would be a sign of a pH that is too high, locking out non-mobile nutrients - Ca, Si, trace elements.

However, there is also damage to the leaves below the growing tips.

And that means that there is something systemic going on. Something is interfering with the plant's photosynthesis, and that's mildew.

The good news is that if treated quickly and swiftly, the plant can be saved. Prune the plant's 1/3 or more lower leaves and branches. This will remove much of the infected leaves, and create much better air flow, especially between the bottom of the plant and the soil. And then spray with something against mildew. This increased airflow will increase the plant's metabolism and make the plant grow faster.

The yield will actually be larger, because more the energy of the plant will go into the buds.
 

aceRimmer

New member
Thank you all very much for the excellent feedback. TanzanianMagic, I'm not smelling anything objectionable at the top of the plants, or from the leaves; nor seeing any visible evidence of mold. But it can't hurt to be safe, so I'll begin treatment a.s.a.p. I've also lollipoped each of the plants as can be seen in the attached images. I did not want to go overboard with the defoliation, so it's still a little dense up top. I'll get a couple of little fans and put them underneath the canopy to promote better air circulation down there, but please advise if you all think I should go further and remove more leaves. One thing I did notice when lollipopping is that the steams do smell kinda bad. I wouldn't say a mold smell at all, just really really pungent, and not a nice smell at all. I don't know if this is normal.


My suspicion was that, of all the deficiencies I had read about, Mg was the most likely, so I'll add some MgSo4 to my next few feeds and see how things go. It could just very well be that simple, seeing as how I had been underfeeding for so long. I'll also take the pH up a few points as advised.



Things haven't really progressed downhill since upping the nuts to full strength, and the plants are still putting on weight, so these changes might be all it needs to take it to the next level. I'll give them a week and see how things are and report back. Again thank you all for your input.:tiphat:
 

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TanzanianMagic

Well-known member
Veteran
Things haven't really progressed downhill since upping the nuts to full strength, and the plants are still putting on weight, so these changes might be all it needs to take it to the next level. I'll give them a week and see how things are and report back. Again thank you all for your input.:tiphat:

Well that's great to hear.

Just a last check, however the leaves in the bottom left of the picture, is that a blurred camera effect, or is that leaf damage? If it's leaf damage, an up close examination would be helpful.

https://www.icmag.com/ic/attachment.php?attachmentid=480388&d=1545692237
 

aceRimmer

New member
Yep, just blurring. I doubled checked and they look super healthy. One thing the colour tempurature of my lights do is make it super easy to spot any variation in colour across the leaves. If I look at the plants under natural light, then even the lightest leaf in those images looks a healthy uniform dark green.



They dropped right after the lollipopping as expected, but I just came back from a day and a half Christmas gathering with the family and they have absolutely exploded. The sensor hanging in the image you linked is now below the canopy.
 

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