Deficiency, toxicity, light stress??? wtf is going on - week 4 flower

[Shimona]

Week 4 in flower running 4seasons 200w LEDs dtw in coco perlite 70/30 blend. Lights are about 20 inches away

Top leaves are yellowing and appear to have withered/become skinny. Whereas the majority of bottom growth seems to be okay or at least not as badly damaged

Watering twice a day, just increased to 3 times, with around 15% run off. Have tested run-off both EC and ph coming out as it should

PH is 5.8 and EC 1.8-2 as per recommendation on label

Currently using Green Planet dual fuel Part A+B

Flushed them a week ago which hasn't appeared to have made a difference. Growth has been stunted significantly. Temps have been hovering around 80 F with humidity around 60%




All help/suggestions greatly appreciated




One frustrated grower!

 

[Bdubs]

Cannabis likes dry back. They enjoy seeing a dry period in their medium. If you water too often you maintain a soaked/wet lower half of the soil. Waterlogging all roots half way down and strangling them making them unable to take in nutrients. Let them dry out to the point where the leafs droop from needing water before you water. If you are staying too moist, you’ll need a long period of not watering to get back on track. Continual watering and water logging causes respiration to stop. Which in turn closes stomata and transpiration stops as well. The plant stops drinking and eating and the leafs will dry and crisp as the plant uses stored moisture to stay alive. They need respiration and transpiration to drink and eat.
This is a watering habit issue.

 

[Bdubs]

Notice some of your leaf edges are curled downward and droopy. That is overwatered.

Notice some leafs are dry and crispy. Heat stress and using stored moisture (due to waterlogging).

Your 60% humidity is too high. It needs to be 45-50 at that stage. With this humidity and watering every day is going to eventually overwater. As a higher humidity will have the plant drinking less from the roots. This is humidity for veg stage and not flower stage. Lower humidity taxes the roots to do the drinking and is desired in flower. Reducing humidity will allow more frequent watering, higher humidity will make you need to water less.

You have multiple issues but it all boils down to environment and watering habits.

Reduce humidity.
Stop watering until the leafs perk up and do not water until they droop after waiting however long it takes for them to go from droop to perk and droop again.

 

[Shimona]

Cannabis likes dry back. They enjoy seeing a dry period in their medium. If you water too often you maintain a soaked/wet lower half of the soil. Waterlogging all roots half way down and strangling them making them unable to take in nutrients. Let them dry out to the point where the leafs droop from needing water before you water. If you are staying too moist, you’ll need a long period of not watering to get back on track. Continual watering and water logging causes respiration to stop. Which in turn closes stomata and transpiration stops as well. The plant stops drinking and eating and the leafs will dry and crisp as the plant uses stored moisture to stay alive. They need respiration and transpiration to drink and eat.
This is a watering habit issue.

Even in coco - i was aware of that being the case in soil but not so much coco coir. If it was nutrient lockout would the run-off not come out higher/lower? I will dry back and hope that they bounce back. Do you suggest reducing feed frequency after dry back?

 

[Shimona]

Notice some of your leaf edges are curled downward and droopy. That is overwatered.

Notice some leafs are dry and crispy. Heat stress and using stored moisture (due to waterlogging).

Your 60% humidity is too high. It needs to be 45-50 at that stage. With this humidity and watering every day is going to eventually overwater. As a higher humidity will have the plant drinking less from the roots. This is humidity for veg stage and not flower stage. Lower humidity taxes the roots to do the drinking and is desired in flower. Reducing humidity will allow more frequent watering, higher humidity will make you need to water less.

You have multiple issues but it all boils down to environment and watering habits.

Reduce humidity.
Stop watering until the leafs perk up and do not water until they droop after waiting however long it takes for them to go from droop to perk and droop again.

Unfortunately its like 100% a lot of the time where i live so even with the dehu cranked 24/7 it can be pretty difficult to get it under 50%.

 

[StoneS]

It looks like too high ec, amoung other problems.
You’re not going to fix those affected leaves for the most part, so focus on old healthy ones and new growth to monitor.

The above isn’t bad info, but it requires a lot more explanation and situational info.

Plants do like dry back, but it is absolutely not essential.
You may run into problems by switching the moisture it sees haphazardly, but this will mainly be ec fluctuations.

I regularly bottom feed a d let plants sit in 1/2 inch of water.
This is not ideal for sure, but it’s easy lol.

Plants create water roots.
How could DWC or Kratky work if they were unable to tolerate standing water.

Also the environmental advice you received is the ‘old school thinking’.
Jungle Boys shows this best.
Plants ‘feel’ the VPD.
Research VPD for deciding your temp and humidity.
1.0-1.4 is standard.
But remember, you have to have the rest of your environment dialed to not run into problems.
No microclimates or standing air.