Yellow spots on cola/sugar leaves?

[GringoStarr]

Hi all. I'm fairly new to growing, and currently just doing autos. I'm on my second run right now, bringing up a couple GHS Northern Lights x Green-o-matic. I also ran this strain on my first grow with almost no problems and great results.

I'm in 60/40 coco running GH Flora (M+B only) in a modified Lucas w some amendments (Molasses, Liquid Kool Bloom) in fabric pots under a Mars II 700w LED. On this run I've been bottom watering every time and only flushed once, when I went into flower. This is an experiment and a change from last time, when I flushed 4 plants every weekend, which is a shit ton of work.

This time around I'm 4 weeks into flower and seeing some yellow spots on the sugar leaves of the cola of one of the plants, and starting lightly on some sugar leave on lower buds of the same plant. The other plant, planted on the same day from the same seed and subject to the same conditions, does not show the spots. Thinking my pH could be out of whack or I could have some salt buildup from too much bottom watering, I flushed both plants today. Jury's still out on whether or not that was effective. Here's some pics. Any light y'all could shed on the situation would be hugely appreciated. Thanks in advance!

 

[Rifleman]

Not sure but maybe these will help. Odd that she looks healthy up to the top. Using LEDs, are you supplementing cal-mag? Hopefully someone with a little more exp will chime in soon.

 

[GringoStarr]

Not sure but maybe these will help. Odd that she looks healthy up to the top. Using LEDs, are you supplementing cal-mag? Hopefully someone with a little more exp will chime in soon.

Yeah, my full strength feedings still have 5ml/g cal-mag.. Yeah the spots are really just on that one cola and a couple others on that plant. The other plant I'm running is completely unaffected.

 

[2clean]

Raise your ph so it can p;ull more sulfur and cal mag

 

[GringoStarr]

Raise your ph so it can p;ull more sulfur and cal mag

Thanks man.

The flush I did before this post might have done the trick, because the yellowing hasn't progressed.. so I guess I'll just wait and see, thanks..

 

[GringoStarr]

The flush I did before this post might have done the trick, because the yellowing hasn't progressed.. so I guess I'll just wait and see, thanks..

Wishful thinking I'm afraid.

 

[Teddy Edwards]

Hi Gringo. Welcome to 420. That doesn't look like a happy leaf. Have you been through this section - it's got useful photos?

Cannabis Plant and Pest Problem Solver - Pictorial

 

[2clean]

looks like overwatering or high humidity..i would calibrate your ph tester and use plain ph water for now. looks like phosphorous def also.

 

[GringoStarr]

Hi Gringo. Welcome to 420. That doesn't look like a happy leaf. Have you been through this section - it's got useful photos?
.

Yeah, that one and others like it. Nothing really jumped out, thanks though.

 

[GringoStarr]

looks like overwatering or high humidity..i would calibrate your ph tester and use plain ph water for now. looks like phosphorous def also.

Oh cool thanks, I didn't see this before. Well, it's definitely not overwatering or high humidity. Humidity here is actually waaay too low right now, about 20-25%.. and I store the pH tester in 7.0 fluid and check it every time I use it. It does kinda look like pics I've seen of both phos and pot defs, but I don't know... the yellow/browning shows up weird and patchy, not really starting in the tips.

Thing is, my other plant, same breeder, same strain allegedy (although it does look to have some phenotype differences), subject to the same conditions right next to it is perfectly fine.

 

[GringoStarr]

Humidity here is actually waaay too low right now, about 20-25%..

Wow. Actually, the rest of the basement is 25%. My grow closet with the radiant heater is 16% rh.
Could that be affecting nute uptake?

 

[Tead]

Your sure it's not heat related? I can't help but notice the bad spots are all on top.

 

[GringoStarr]

Your sure it's not heat related? I can't help but notice the bad spots are all on top.

Yeah, it's possible.. I guess the temps been up there as well, around 90F. I'd left the hygrometer in the room where I was drying my last haul, and just spaced putting it back in w the plants.. my environment had been stable for so long. Sloppy, I know.

 

[Tead]

I totally start getting damage at 90f. Had it happen ever so lightly just the other day.
Your damage is enormous compared to my few leaves... so that makes me wonder if it's something else, but then again, if you hit 95f, perhaps.... and all the damage is in the top. hmmmm....

 

[Tead]

give us a close up of your lighter damaged leaves.... down a bit from the top. I see some in the lower right quadrant of your first photo.

 

[GringoStarr]

I totally start getting damage at 90f. Had it happen ever so lightly just the other day.
Your damage is enormous compared to my few leaves... so that makes me wonder if it's something else, but then again, if you hit 95f, perhaps.... and all the damage is in the top. hmmmm....

Also, I'll bet they're not thrilled about the low rh.. could be more than one factor involved making the environment inhospitable. I put a bunch of water pans down there and lowered the heat this morning, but I'm afraid the damage is done with that one plant. I'll probably chop it in a week or two and get what I can out of it.

give us a close up of your lighter damaged leaves.... down a bit from the top. I see some in the lower right quadrant of your first photo.

Ok.. you're talking about the first photo in the second set right?

 

[Tead]

Ok.. you're talking about the first photo in the second set right?

First photo in first post of thread. Cola in lower right with less damage... but still showing damage.

 

[Tead]

Here are some examples of my VERY LIGHT heat damage. I clipped some leaves... they don't recover. These were still left. It's been about 3 weeks since my heat incident.
Can you draw any similarities.
Another symptom of heat burn is curl around the leaf edges. You can see some if it in my photos. Do you have any curl around the side spikey part of your leaves.

 

[Tead]

I'll probably chop it in a week or two and get what I can out of it

Yeah.... it's rough... but sometimes best. Decaying material can be problematic in many different ways. None of the damage will recover.
Sux.
In a 'glass half full' spirit.... Got any replacements on hand? Perhaps their time to shine is near.

 

[Tead]

I looked at your second set of pictures again. I feel a bit stronger that it might be heat damage. The way it's evenly damaged around the high spots of the leaves fading as it get to the lower parts of the leaves... not as patchy as I would expect a chemical burn to be.
Do you measure your temp at canopy top height? Perhaps a measure from right in the plant at the very top.