Yellow leaves with brown spots in Flower

Newbie grower here, thanks for your help. Day 16 Flower. Getting many yellow leaves with brown spots - mostly the large fan leaves are affected. See photos - thanks.



How long has this problem been going on? On and off for about a month
What STRAIN are you growing? WWXBB and some type of Blueberry
What was the establishing technique? (seed or clone?) Seed
What is the age of your plants? Day 16 Flower (in Veg for 8 wks prior)
How long have they been in the soil mixture they are in now? 6 wks
How Tall are the plants? 9-12' (I've done quite a bit of LST to keep them short)
What PHASE (seedling, vegetative or flower) are the plants in? Flower
What Technique are you using? (SOG, SCROG etc) n/a
What size pots are you using? (Include how many subjects to pot): 3 Gal.
What substrate/medium are you using? What brand of soil mixture are you using?(percentage of perlite, vermiculite...etc?) FF Ocean Forest with about 1/3 perilite
What Nutrient's are you using? Roots Organic Buddha Bloom
How much of each nutrient are you using with how much water? As above. *Knowing the brand is very helpful*: 1-2 tsp/gallon every other feeding.
How often are you feeding? Every other watering (watering every 4-5 days)
If flowering, when did you switch over to using Bloom nutrients? Right after flowering.
What order are you mixing your nutrients? (example: veg nutes 1st, bloom 2nd ect) n/a
What is the TDS/EC/PPM of your nutrients used? Unknown
What is the pH of the "RUN-OFF"? 6.8
What method of pH test was administered? Using Strips? pH pen? Pen
How often are you watering? Every 4-5 days
When was your last feeding and how often are you feeding? Couple days ago
What size bulb are you using? 2 300W LED's and 3 small CFL's just for heat
What is the distance to the canopy? 15" (just raised LED's from about 10")
What is your RH Factor? (Relative Humidity): 25%
What is the canopy temperature?
What is the Day/Night Temp? (Include fluctuation range)? 73 day, 59 night
What is the current Air Flow? (cfm etc.): Exhaust fan on lowest setting.
Tell us about your ventilation, intake exhaust and when its running and not running ? Exhaust when lights are on.
Is the fan blowing directly at plants? Above them.
Is the grow substrate constantly wet or moist? Moist.
Is your water HARD or SOFT? Don't know
What water are you using? Reverse Osmosis (RO)? Tap? Bottled? Well water? Distilled? Mineral Water? Tap, pH to about 6.5
Are you using water from a water softener? no
Has plant been recently pruned, cloned or pinched? No, LST though
Have any pest chemicals been used? If so what and when? no
Are plant's infected with pest's? No

Soil is not my forte. That being said, they look underfed with a very minor pH problem.

Night time temperature is too low imo... Can you warm the intake?

I would guess Calcium and magnesium . Try a liquid supplement for now.
Add gypsum and a little dolmite lime for long term.

Peace GG

OldBeans said:

Night time temperature is too low imo... Can you warm the intake?

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Thanks. Not easily. 59 at night is too low?

gorilla ganja said:

I would guess Calcium and magnesium . Try a liquid supplement for now.
Add gypsum and a little dolmite lime for long term.

Peace GG

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Thanks.

I've been thinking it could be Calcium deficiency, just surprised this would happen in soil. I have some CalMag liquid - will give some of that next feeding.

Do others agree I should feed more? I'm using Roots Organic Buddha Bloom.

Michael49 said:

Thanks.

I've been thinking it could be Calcium deficiency, just surprised this would happen in soil. I have some CalMag liquid - will give some of that next feeding.

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I've gotten a pretty strong impression that once soil temperatures get too low the roots can no longer take advantage of whats available to them in the soil efficiently.

PDX Dopesmoker said:

I've gotten a pretty strong impression that once soil temperatures get too low the roots can no longer take advantage of whats available to them in the soil efficiently.

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I see. I just didn't think 59 degrees would be cold enough to do this.

Michael49 said:

Thanks. Not easily. 59 at night is too low?

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Yes, it's very low, I've found strains with blueberry genetics in them are the most sensitive to lights off temps. Ideally 20c/68f is the minimum temperature for lights off imo

If you can't warm the intake, can you insulate the pots with bubble wrap? Or slow your extraction down for lights off??

I used to feed the outtake from my veg tent into my flower tent and that always worked for me.

I don't think giving more food will make a difference with lights off temps so low, the root all will be a few degrees colder than ambient temps

Good luck friend!

When I go below 67F in hydro, I have the same uptake problem.

OldBeans said:

Yes, it's very low, I've found strains with blueberry genetics in them are the most sensitive to lights off temps. Ideally 20c/68f is the minimum temperature for lights off imo

If you can't warm the intake, can you insulate the pots with bubble wrap? Or slow your extraction down for lights off??

I used to feed the outtake from my veg tent into my flower tent and that always worked for me.

I don't think giving more food will make a difference with lights off temps so low, the root all will be a few degrees colder than ambient temps

Good luck friend!

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Thanks for the input - I will try to increase the nighttime temps.

I watered today. 1 1/2 tsp/gallon of Organic Roots Buddha Grow (thought they might need a little nitrogen) plus 5ml/gallon of CalMag. I'm trying my best to raise the nighttime temps.

Here's a photo of several dying leaves that I removed to see if this helps ID the problem and updated photos of the girls.....

Forgot to mention that I recalibrated my pH meter last night and it was reading high!! So when I thought I was pHing my water to 6.5 it was probably more like 7.5!!!

Sure looks like a phosphorus deficiency...

Your problem looks like it has gone away, your newer growth is healthy and green.
Those older damaged leaves all need to be removed, once in that condition they will never improve and just take away energy from the plant. When you cut away all those crappy leaves, your plants will look just fine. Don't overfert and add a little calmag in a couple weeks from now.

I would suggest a light phosphorus feed, say 0.5% phosphoric acid. Do it light on one side of a plant, on one branch. That is how you learn.

The give away on a P deficiency on this leaf is the fact that the strong chlorosis does not obey the veins. Phosphorus is the only element that will do this. Most everything is margins, interveinal, etc. I would also bet you would see a big response to some micronutrients like Mn for example. Again, do one branch and watch what happens.

A good one to confirm positive response is to test petioles, after washing of course, with a refractometer. If the plant got a response, the brix will increase, in about 24 hours or so.

Also, if the P response shows up, that branch will start praying heavy.

Experiment my friends!

Douglas.Curtis said:

When I go below 67F in hydro, I have the same uptake problem.

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Thats pretty much the same number I've noticed for soil temperatures. Once if goes into the mid-lower 60s things seem to start shutting down pretty quickly. Sitting right at the edge of disaster in the upper 60s seems to be where the flavor is at.

Something I found with a closed room at night is that high humidity during lights out can make temps stay much lower than they should be.

I remember a case when night temps in a closed room would always be 5-8 degrees colder than rest of rooms in house. . . put a dehumidifier in during lights out, and viola, temps jumped up above 70 degrees.