Splotches on leaves: help me to resolve the mystery?

[MarcusAurelius]

Over the past few weeks ago splotches like this (1) and this (2) appeared on the leaves (old growth) and leaves turn yellow/brown/black and fall off and dry up. There is red in the stems and leaves curl upwards. Problem appeared when I started flowering. I thought first it was a phosphorus deficiency and gave them more phosphorus but the problem didn’t disappear... Then I realized it could had been a nutrient lockout so I flushed my plants so that the EC coming through the pots where roots are was about 0.16 (water without nutes here is 0.13 EC). After that I gave 'em nutrients + PK Boost so that I got EC around 1.7 and have maintained it around 1.6. 3rd week of flowering currently.

The leaves still show sign of splotching, yellowing, dropping.. the same symptoms. So I've been wondering what the heck this is and trying to have a solution before I lose all the bottom leaves. I've been lollipopping them so I don't have too much of them left. I had a gnat fly infestation few weeks earlier which was a pain in the ass, I treated my plants and pots with Neem oil spray... have not seen those buggers in half-a-week now. I've ordered some mosquito dunks which I'll apply to my medium when they arrive so I can ensure they are gone for good. So what is going on here? Nutrient lock-out, phosphorus deficiency or phosphorus deficiency appearing because of fly gnats?

I also have different kind of new splotches like this (3) on the upper growth. Any idea what is it? It appears to be a different issue than what is going on at the lower leaves. I'm growing in hydro Atami Wilma (re-circulating) top-feed hydro and using clay pebbles as the medium. pH is correct and has been correct throughout the grow, I've been managing it between 5.5 - 6.4 (the manufacturer recommends 5.8 - 6.4 pH as optimum in this hydro).

Any insights?

 

[1ne eye]

In the 3 picture it almost looks like a potassium deficiency. But I'm no expert so I would wait until more people take a look and chime in. The damaged leaves won't come back.

 

[Alafornia]

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[MarcusAurelius]

Strain - Pink Kush
Sativa/Indica - Hybrid
How many plants - 4 plants
How many weeks flowering - Currently in flowering stage, 3 weeks now
Indorr or outdoor - Indoor
Type of grow - Hydro
Reservoir size - Reservoir 50 litres
Reservoir temp - Reservoir temperature 20 C
Medium - Clay Pebbles
System - Atami Wilma, re-circulating top-feed hydro (large)
Are lights cooled - No HPS, no need to be aircooled
Lights & wattage - GC16 (Greenception) COB LED light, power consumption 480W and equivalent to 600W HPS + TGL Star 60 (COB LED light) power consumption 55W, equivalent to 130W HPS
Is air cooled - Some days, it's very expensive to run AC 24/7 to drop ambient temps in the house so I try to avoid it unless absolutely necessary but there is exhaust in the tent that pulls hot air out
Temperature - the meter says 30 C, but I do think the meter is faulty since there are no signs that indicate slow of growth, no cupping or other symptoms of heat stress... I also provide the plant CO2 to water reservoir with tablets + silicon + and give them Vitalink Chill which makes them more heat-resistant along the fact their roots are in ideal temperature which makes me think that's why there is still good progress with flowering
Relative humidity - 45%
Pests - Had fly gnats, not sure are they still around, going to nuke 'em with Mosquito dunks nevertheless
Watering - 3 times a day on a timer
Nutes - I use IONIC's nutes according to labels maintaining 1.6 - 1.7 EC. Products I use are: Hydro Bloom, Superdrive, Green Fuse Bloom, PK-Boost, Silicon.
Only products not by IONIC that I use are Piranha and Vitalink Chill. I have perhaps given too much Piranha for the plants but I highly doubt it's an issue.
Size of grow room - 1m x 1m x 2m

 

[1ne eye]

How do the roots look?
Water temperature? When you say your watering them three times a day, just wondering why if this is dwc you shouldn't have to water except to top up the res.
Are you using RO water? Cal / Mag.

 

[AdaminCO]

PH?

 

[Chris Scorpio]

Sounds like top feed DWC which I'm not a fan of

Probably a big rock wool cube being saturated too

 

[Alafornia]

I also provide the plant CO2 to water reservoir with tablets + silicon + and give them Vitalink Chill which makes them more heat-resistant along the fact their roots are in ideal temperature which makes me think that's why there is still good progress with flowering

I've seen people making sure their roots get O2 but not CO2. Is this standard?

 

[Alafornia]

PS At what strength are you feeding the nutes? Full, 1/2, 1/4?

 

[MarcusAurelius]

How do the roots look?
Water temperature? When you say your watering them three times a day, just wondering why if this is dwc you shouldn't have to water except to top up the res.
Are you using RO water? Cal / Mag.

Not a DWC. Water temperature 20C. It's a top-feed hydro, the roots are in the pots with the medium. As you can see, because of this I simply cannot check the roots without pulling the whole plant out of the medium. Using tap water. Tap water is not RO, as the EC of my earlier flush implies..

 

[MarcusAurelius]

PH?

5.5 - 6.4... the pH moves pretty fast, if I set it at today at 5.5 and go tomorrow check it is around 6.4.

 

[MarcusAurelius]

-

 

[MarcusAurelius]

Sounds like top feed DWC which I'm not a fan of

Probably a big rock wool cube being saturated too

No rock wool, I used rapid rooters.

I've seen people making sure their roots get O2 but not CO2. Is this standard?

I'm using GIB CO2 tabs which specifically recommends adding to the reservoir... I just read online that some places recommend putting it in a bowl with water in the grow room and not to the reservoir. I'm going to leave them out of reservoir for now to rule that thing out, but as the package recommends it I'd imagine it is not dangerous to plants?

PS At what strength are you feeding the nutes? Full, 1/2, 1/4?

Around 3/4 now, I use around 5ml/l IONIC's Bloom and the max. is 7ml/l.

 

[AdaminCO]

5.5 - 6.4... the pH moves pretty fast, if I set it at today at 5.5 and go tomorrow check it is around 6.4.

Have you tried adding seaweed or kelp? That may help stabilize your PH. It will naturally drop it some, but I’ve found in my premixed jugs, it holds my PH in range a bit longer than not having it.
I’m also in an organic soil mix so ranges are a bit different for me. Not too much of concern.

 

[AdaminCO]

Have you tried adding seaweed or kelp? That may help stabilize your PH. It will naturally drop it some, but I’ve found in my premixed jugs, it holds my PH in range a bit longer than not having it.
I’m also in an organic soil mix so ranges are a bit different for me. Not too much of concern.

You might want to bump your temp and RH too.

 

[MarcusAurelius]

Have you tried adding seaweed or kelp? That may help stabilize your PH. It will naturally drop it some, but I’ve found in my premixed jugs, it holds my PH in range a bit longer than not having it.
I’m also in an organic soil mix so ranges are a bit different for me. Not too much of concern.

Isn't organics like seaweed or kelp off-limits due hydroponics?

 

[MarcusAurelius]

You might want to bump your temp and RH too.

Thanks for the diagrams, I'll drop temp and RH.

 

[Alafornia]

No rock wool, I used rapid rooters.



I'm using GIB CO2 tabs which specifically recommends adding to the reservoir... I just read online that some places recommend putting it in a bowl with water in the grow room and not to the reservoir. I'm going to leave them out of reservoir for now to rule that thing out, but as the package recommends it I'd imagine it is not dangerous to plants?



Around 3/4 now, I use around 5ml/l IONIC's Bloom and the max. is 7ml/l.

Do you have some air stones bringing O2 to your roots?

 

[MarcusAurelius]

Do you have some air stones bringing O2 to your roots?

Yes, I do have airpump + airstone which bring oxygen to reservoir. Wilma doesn't necessarily need airpump or airstone.

 

[MarcusAurelius]

Sounds like top feed DWC which I'm not a fan of

Probably a big rock wool cube being saturated too

I wish it was DWC as it isn't, in Wilma the roots are inside to pots that are automatically watered with timer using top-feed... I'm likely to buy a DWC when I start my next project as I'm neither a fan of this hydro system. I have not converted this to any kind of DWC by drilling holes since when I got the hydro system I didn't know if I was going to mess with the drainage speed of the pots if I drilled more holes. Gotta say in retrospect I wish I'd have since the drainage speed is not very fast + the drains of the reservoir collect a lot of water but I think I'm not going to drill new holes at the midst of this project now.