Black dots spreading and growing larger

Hey all. Long time reader, first time user. Firstly, thank you all for your passion in sharing knowledge. It's really wonderful seeing how many people here are growing what they love and sharing it with the community.

I have 2 BC big buds growing in a small pc grow box. They are 5 weeks into veg, are on a 16/8 cycle and growing in a soilless medium (pro mix). Give it water PH'ed at 6.2-6.3.



It gets water every 2.5 days, and 1/4 strength nutes 20-20-20 every other watering. The yare under 3 26w CFL's about an inch to an inch and a half away from the light.

Everything has been going smooth as butter until a few days ago where the black dots on the bottom of the plant began growing more numerous, spreading to the top slowly and growing larger in size (the spots).

Here are images. I'm convinced that they are not pests because I can't see any evidence of webbing or the mites themselves. I believe it's a nute issue because I'm watching the spots develop over time, getting larger and am not quite sure poop of an insect would do the same.

I just want to save my plant before it's too late. Your wisdom, experience, guidance, and comments are very very welcome and appreciated.

Here are images taken a few moments ago of my two plants. What do you think? The only thing I can think of is Magnesium, calcium, or manganese based on images I've found online.

Forgot to add that my temps avg at 79 and humidity at 50.

I'm no expert, but that looks like calcium deficiency-

https://www.icmag.com/ic/showthread.php?t=231387

Over watering, low ph & gnats make it worse. Maybe root aphids if you're growing from cuts.

Nice fingerprints.
I'm no expert either, but I think Jhhnn is right.

Stitch's guide to sick plants
https://www.icmag.com/ic/showthread.php?t=11688

Thank you so much guys. It's nice to have support and also know that I'm learning a little something.

I will go to the local hemp store and find some calcium for these babies.

If left untreated, would this kill the plant?

If left untreated it will definitely be a big issue

Calmag, calimagic, dolomite, azomite. These items all have calcium in it

As Jhhnn suggested, it could be your soil ph, maybe your soil is too wet. Do you lift your pots to tell if they need watering by judging their weight? Adding more calcium may not be the best answer (but it is a quick option to try). Is your tap water high in minerals? It might already be full of calcium.

never used promix, but for the most part a "seed starting mix" isn't going to have much nutes in it, and quarter strength nutes are barely more than whats in seed starting mix. your plants are hungry. the end. have a nice day

oh yeah, that's not calcium. that's phosphorous deficiency. if you let it go a few more days those brown and purple spots are gonna dry up and turn yellow then curl up and the makes holes or the whole leaf will dry out and shrivel. calcium looks like little rust spots randomly mostly near the edges.

Crusader Rabbit said:

As Jhhnn suggested, it could be your soil ph, maybe your soil is too wet. Do you lift your pots to tell if they need watering by judging their weight? Adding more calcium may not be the best answer (but it is a quick option to try). Is your tap water high in minerals? It might already be full of calcium.

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I don't know my soil PH. Should I be measuring the runoff? Which leads me to my next noob question. As I am growing in soilless mix, am I correct in aiming for a watering PH of 6.2? If this is correct, is it more important that my runoff reads at 6.2 or that the watering solution be at 6.2? If the runoff is more indicative of what's going on, should i simply buffer my watering solution until the runoff reads the correct amount?

I only water once the soil is both dry to the touch, the yogurt container is light and a slight cracking feeling when gently squeezing the container around it's sides. The leaves also lose their perkiness, and this happens at every 2.5 days.

And yes, the mix I'm using doesn't have much in terms of nutrients. The plant was going off of mostly the cotyledons the first few weeks and even then I was getting minor nute burn on the tips of leaves . I still get them a bit too, or perhaps it's actually a deficiency. I will try increasing the strength of the nutes to half strength two waterings from now as they were just fed. Hopefully that will resolve the phosphorus def.

stihgnobevoli, are you saying that there is no calcium issue that you can see? Simply using the link posted, I do see similarities between the black dots shown on the calcium deficiency and what one of my plants is exhibiting. Does your experience tell you that this is most certainly phosphorus and a calcium supplement is not required? Was going to go and buy some today but will await your expertise.

Thank you again! Your help is invaluable. Here are a few more photos of the plants in their "glory" lol. Still haven't seen the sex of one of em.

Fun but sad story. On NYE, slightly drunk, I was putting the plants to sleep and put the room heater slightly too close to the case. When I came to check on them briefly before going to be myself, I noticed that the temp reader was around 120 degrees (maybe higher actually) and the plant that was closest to the heater (the one with 3 main stems now) had more than 50% of it's leaves completely burned. During that week 90% of it's leaves dried and fell off, I thought the plant was done for. Instead, the main stem broke off near the top and two main stems emerged near the base of the plant. Such resilient things...

i don't see any calcium signs, just hungry plants. up the dose a little you should be fine. didn't realize you were in yogurt cups.

Thank you!

Might I bother you with the question about water PH in my previous post? Would love your insight.

this helps me sometimes when I'm not sure. my is add a foliar of botanicare's calmag. it has nitrogen along with the cal mag. calcium is kinda tricky in that it looks the same whether you have too much or not enough. I'm not sure if it's nitrogen because it appears to me to be yellowing from the top down instead of from the bottom up to the top. this is what I'm talking about. watch these videos. they're short and great info for understanding this sorta thing. try a ph of 5.8

http://www.greenhousegrower.com/vid...-identifying-nutrient-deficiencies-made-easy/

http://www.greenhousegrower.com/vid...ying-nutrient-deficiencies-made-easy-part-ii/

http://www.greenhousegrower.com/vid...-identifying-nutrient-deficiencies-made-easy/

Great links, will have a study session today. Thank you ladylucky! Last question is just in regards to PH going in vs PH going out. Which one is more important in hitting PH of 5.8?

Your girls look really starved. I think you should start by feeding them a bit heavier and see where it takes you from there

Yoghurt cups huh? If you let the soil/media get too dry, it can stress the plants too. Easy to do in small containers. Plants get lockout when the moisture becomes real limited and any dissolved nutrients become concentrated. Stihgnobevoli is right about your plants looking hungry. They aren't very green. I bet they're starting to get root bound too. I know you have low head space in your grow box, but if you can find some wider containers your plants would appreciate having some media on the outer portion of their packed root mass. Do you have a Smart and Final or other restaurant oriented bulk food store nearby? Maybe you can find something you'd like to eat in a bigger squat container. Walk the isles looking at the containers the food is packed in. A 3lb cottage cheese tub would work. With chips and salsa it makes a decent dip. Ideally you'd find a rectangular shape that fills half your box. The bottom half of a gallon milk jug might be perfect.

Crusader Rabbit said:

Yoghurt cups huh? If you let the soil/media get too dry, it can stress the plants too. Easy to do in small containers. Plants get lockout when the moisture becomes real limited and any dissolved nutrients become concentrated. Stihgnobevoli is right about your plants looking hungry. They aren't very green. I bet they're starting to get root bound too. I know you have low head space in your grow box, but if you can find some wider containers your plants would appreciate having some media on the outer portion of their packed root mass. Do you have a Smart and Final or other restaurant oriented bulk food store nearby? Maybe you can find something you'd like to eat in a bigger squat container. Walk the isles looking at the containers the food is packed in. A 3lb cottage cheese tub would work. With chips and salsa it makes a decent dip. Ideally you'd find a rectangular shape that fills half your box. The bottom half of a gallon milk jug might be perfect.

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hehe yeah. Awesome, you've actually said something I've been thinking about over the last few days and that's getting a slightly shorter but wider pot for the plants and was having a struggle cause the lady and i couldn't figure out anything that we buy that might be the perfect fit. Lol. Will look for something more appropriate on my next trip to the grocery store.

Sorry to be a pest, but waiting to hear a response to the PH question regarding my soilless mix from my previous post.

Many thanks!

This morning I gave them some water and food and am hoping I did things right. I read so much conflicting information about how to PH for the pro mix soilless medium.

I saw a wonderful chart showing that I should be going for 5- 5.8 ph so I did just that. Here are the results with runoff. Am I doing this correctly? They are in week 6 of veg but have been given very low nutes ( as seen by my previous posts )



Plant 1:
PH 5.8 / 380 ppm nutes (20 20 20)
Runoff: PH 5.0 / 480 ppm

Plant 2:
PH 5.8 / 380 ppm nutes (20 20 20)
Runoff: PH 4.7 / 540 ppm

google "slurry ph test"

its the most accurate way. make a pancake batter type consistency of soil and RO water (I think. I don't ph in organics) and then you wait 30 mins and then stick you ph pen in there. think you can do it for the ppms too. I think you may need to flush her again but maybe this bump will find someone who can help ya a bit better. until then, google the slurry test.

even if it's just a runoff test your ph shouldn't be coming back that low if it went in at 5.8. ppm are higher than when what you put in. you should do a slurry test but i think the K in coco is locking out your nutes.