Hydroponics - troubleshooting leaf spots please help

Terminatorkader

Well-Known Member
Hi just started my first dwc. I’m only doing two plants in five gallon buckets. Distilled water with fox farms hydro nutrients in a mars hydro grow tent / two tsw-2000 lights. Two fans a small digital heater and humidifier in the tent. Each bucket has a 6” air disc powered by a Vivosun commercial 32w air pump. I added two tablespoons of food grade 3% hydrogen peroxide to each bucket. Plants are ending week 3 strain is super lemon haze.

My question is, old leafs are getting brown spots. Most of the leaf and stem are green. Ph is in the 6-6.3 range through the day. TeMps are at 68 at night to 74 in the day. Humidity is currently 32%. I mix each bucket the same. Keep each bucket at same ph but one looks like it’s effected more than the other. My ppm is at 1360 -1385 which is in the range for fox farms solution. New growth looks ok and hoping it stays that way.

What are you guys thinking is off? My roots look very nice. Pictures below. The plant with the brown tint roots is not showing as much of these spots as my plant with whiter roots.

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Rexer

Member of the Month: April 2021, Feb 2022 - Photo of the Month: July 2021 - Grow Journal of the Month: Nov 2021
Hi @Terminatorkader

I see your using H202 and no beneficial microbes....I'm assuming your goal is a sterile grow.

If so, that's no where near enough h202 to keep harmful bacteria down.

Are you using food grade (recommended for hydroponics) or stuff from the pharmacy?

Ph to 5.5, let drift to 6.3, then reset to 5.5
 

Rexer

Member of the Month: April 2021, Feb 2022 - Photo of the Month: July 2021 - Grow Journal of the Month: Nov 2021
Hi foot grade. 3%
I'm assuming spell check got to ya :laugh2:

Food grade is a much higher percentage (ballpark of 28%).

Pharmacy comes at 3%.

I'll come back in a bit and drop some reading for you on the subject (just gotta get something done asap).
 

Rexer

Member of the Month: April 2021, Feb 2022 - Photo of the Month: July 2021 - Grow Journal of the Month: Nov 2021
Thanks!!
The problem, and I'm no chemist, that I see is the dilution.

Two table spoons of 3% in roughly 5 gallons does squat in my books. Doesn't mean I'm right.

Take a good read in this post I did for another member.

Post in thread 'First time grow in DWC' First time grow in DWC
 

Rexer

Member of the Month: April 2021, Feb 2022 - Photo of the Month: July 2021 - Grow Journal of the Month: Nov 2021
Hi there’s only 2.5 gallons in each but they are in 5 gallon buckets.
Have you had a chance to read that link?

Generally your aiming to have your solution sitting at 3% h202.

Taking a 3% solution, adding two tablespoons worth of 3% into 2.5 gallons comes out to such a diluted amount it's negligible. Seriously, you could have your plant sitting directly into a tub of that stuff, then you would be at the correct dilution for it.

The spots on your leaves look like adding some cal mag might sort out. Do you have any cal mag additives?
Sorry, I know that's the reason of your post.

It's your roots that worries me. Some Z7 or Hygrozyme would also help them, I'm just worried you might have root rot starting.
 
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KingJohnC

Member of the Month: June 2013 - Member of the Year: 2013
The plant leaf damage is caused by nutrient lockout too high pH levels preventing the plant from accessing usable forms of the nutrients. The plants leaf tips are healthy indicating the nutrient strength is not excessive. It is a mobile nutrient deficiency the plant is attempting to use stored nutrients from older vegetative growth to supply energy for new vegetative growth.

The nutrient solution pH is rising too high and causing the nutrients to bind to more complex bonds more difficult for the plant to access. You want pH 5.8 for hydroponic nutrient mixtures.

Can you please list all the individual products you are currently using and in what quantity per gallon, the water sources starting pH and the order you are adding the nutrients to the water source to determine if there is also an unwanted interaction causing the nutrient lockout?

Is there a reason for running the reservoir volume low? The total volume of the nutrient mixture largely provides pH stability for the cannabis plants requirements to access and use the elements in the nutrient solution.

If you are able to, spray off the brown slime coat from the roots as it is may cause root rot.

Can you provide some new photographs of the upper new vegetative growth for diagnosis of the nutrient lockout?


You want pH 5.8 for hydroponic and soilless (peat moss and coco coir) and pH 6.5 for soil.

Here is a nutrient availability chart

full



Here is a cannabis leaf deficiency chart

full



here is the Cannabis Plant and Pest Problem Solver and the Plant Abuse Chart

Cannabis Plant and Pest Problem Solver: Pictorial

Plant Abuse Chart
 

Terminatorkader

Well-Known Member
New growth looks perfect. Not all leaves are effected. Possible leaf septoria? Seems to start with yellow dot/dots. Below is nutrients I’m using. They are just finishing up week 3. All parameters listed in original posting. Pictures of charts I referenced. So currently only added what is on chart for week three plus 2 tablespoons of 3% food grade hydrogen peroxide.

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AdaminCO

Well-Known Member
New growth looks perfect. Not all leaves are effected. Possible leaf septoria? Seems to start with yellow dot/dots. Below is nutrients I’m using. They are just finishing up week 3. All parameters listed in original posting. Pictures of charts I referenced. So currents only added what is on chart for week three plus 2 tablespoons of 3% food grade hydrogen peroxide.

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To me you have two things going on.

You’re magnesium deficiency is what has/is caused/causing the rusty looking spots. I didn’t see any mention of a CalMag supplement. You might look into a CalMag supplement, or……

It could be as simple as under feeding. The color of the leafs are a bit lighter, generally indicating they need to be feed heavier.

You really need to get your pH to 5.5-5.8.
6.0-6.3 barely catches the prime pick up range. 5.8-6.1 is key.

What’s the temp of your reservoir?
 

Terminatorkader

Well-Known Member
Reservoir temp ranges from night to day. Seems to be at night 69 and day 74.

I’m due for a reservoir change. I’ll add a little cal mag when I do and see if that helps. The ph chart I was using for reference is attached below. It’s why I was targeting a range of 6 to 6.3. I will drop it to a lower range then when I do my reservoir change tomorrow. 5.8 to 6 then??

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AdaminCO

Well-Known Member
The previous leaf damage won’t turn back to green, but don’t remove the leafs until your sure you’ve corrected the issue. Right now you’re plant knows where to find the stored Mag, so keep it there for it to use.
 

AdaminCO

Well-Known Member
Reservoir temp ranges from night to day. Seems to be at night 69 and day 74.

I’m due for a reservoir change. I’ll add a little cal mag when I do and see if that helps. The oh chart I was using for reference is attached below. It’s why I was targeting a range of 6 to 6.3. I will drop it to a lower range then when I do my reservoir change tomorrow. 5.8 to 6 then??

BE15D29B-F78C-4902-91B5-4A80B2485A1D.jpeg
5.8.
Mix the CalMag into the reservoir before you mix anything else.
Is it 2-0-0 or 1-0-0?
 

AdaminCO

Well-Known Member
Okay. I have CalMag+ so it has more N. After you try the CalMag, if you don’t see them green up some, I’d recommend bumping your nutes up. The feed chart is a guideline, your plant looks like it wants more.
 
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