HELP! GSC Auto - Curling, Black/Brown Spots, Canoeing

[Kristie25]

Hi All


​​​​​​My GSC Auto's are about 2.5 months old and recently (~8-9 days ago) went through a bit of heat stress with a 30C (90F) day (must have been hotter in their room but was on holiday at the time). When I got back some leaves were damaged/yellowed or with brown spots and about 80% were canoeing up. They had also grown up into the light 🥲.

Have kept the surface temp of the leaf at 23C (74F) since then, humidity 55-60% with a light fan blowing over them. Water every 2-3 days depending how dry they've become. They have 2 75W CFL's and a 75W LED board. I've tried moving the lights further away and tried starting to feed more potassium (just started with first pistils at branch junctions. But it seems to definitely be spreading/progressing.

They are in a perlite/canna terra mix as a medium. I've previously fed them half the recommended amount of a seaweed based tomato fertilizer every 2nd or 3rd watering and gave them trace elements once or twice.

I lost my previous plant just before flower, please save my babies. (Pics attached).

-Thanks, Kristie

 

[ChadWestport]

Heat is always the first thing to check, you've done that. What I see is a problem with the Ph of your soil. The brown dots in pic 2 usually are a sign of calcium deficiency but the other burning on the margins and tacoing leads me to suspect an issue with the root zone.

When you water, do you Ph it before adding and if so, what are you Ph'ing it at?

When you water, do you get run-off from the bottom? If so, do you collect it so the roots aren't marinating in it?

What size container are you using?

 

[CaptainWiese91]

Too much potassium can lower your soil PH really bad. And give cal mag deficiency. So be of aware of that .
do you monitor the Ph? You don’t need to collect the run off, let it evaporate if you can. My pots are on bamboo stick in the saucer so they are elevated from the run off water, just waste of time to collect it.

I bet my two cents on this taco is from the heatwave you got in your holiday. And the leaves will never return to normal, so no need for keep looking at them. If you have the environment in control then this is all you can do.

and from the pictures I clearly see too much potassium

 

[Kristie25]

Oops! So much to remember haha.

Yes I do pH the water before adding it to the plants, pH it to 6-7 with lemon juice (tap water here is a bit basic).

I normally collect some run off and double check the pH but otherwise it just runs down the drain directly under the pots. They're 4.5L, wanted to put them in bigger but couldn't fit them in the space 😢.

 

[Kristie25]

Yeah I check the water pH before I water then adjust and measure the run off again before it goes down the drain under the pots. Ah I see I thought they would open back up once it cooled off, oops.

Huh strange, this is the first time I've upped the potassium and only gave them 1/2 dose. Previously every couple of waters I've given them half of the seedling dosage of my other seaweed fertiliser. It's NPK is 14:1.4:8

 

[CaptainWiese91]

That is a really High N in that ratio also..
is that a flower fertilizer or just a Norma ?
Most autos don’t need so much nutrients like photos strains.

Give it plain water for a couple of weeks. More nutrients won’t help a plant, when the plant is sick.

 

[Kristie25]

Yeah just a normal fertilizer for vegetables not specifically for fruits or blooms or anything. I have another for indoor plants that is 1.3:0.8:2.1 but this was the one I used on the previous plant which seemed to burn it and it later died. Yeah just gave it plain water about a day after I added the potassium (saw it getting worse) and it's been about 2 days since then. Hopefully they dry up soon so I can flush them out again 😢 don't want to over water now too

 

[CaptainWiese91]

My advice is, buy a special fertilizer made for cannabis. It’s bulletproof when you are newcomer to the hobby.
But hey! You learned something and that is experience! I killed 10 plants before I even made it to a harvest when I started growing for many years back

 

[ChadWestport]

If you are in soil, try getting to the 6.3-6.8 Ph range. The difference of a 6.0 to 7.0 is 100 times difference, so keeping it closer to a fixed number can help Ph swings in the soil. Lemon juice can be effective, but the sugars in it also can attract insects or create conditions for fungus. If you can order online or go to a flower store, they should all carry Ph up and Ph down solutions. These offer a little more stability when fixing the water Ph. Letting the runoff go down the drain is fine for the garden.... but the Sustainable AG professional in me is scolding you for putting fertilizers down the water system. Not very environmentally friendly.... but I'm just me, not judging

 

[CaptainWiese91]

Never had bugs in my soil with use of citric acid ??
Neither fungus, never heard of that..

 

[ChadWestport]

You very well could be right, you have personal experience with it. I've never used it, a bottle of Ph adjusters is $10 and 5 miles away. Jorge Cervantes - Cannabis Encyclopedia is my source on that one. He's generally a great source, but nobody is always right.

 

[Kristie25]

Hey y'all,

I've watered with the tiniest bit of trace elements (calcium, iron etc) and plain pH'ed water 2 days ago and this is what they look like now. The new growth seems to have white tips that then turn brown and the spotting is on another leaf too now. Theyre also droopy on top. Anything else I can do besides wait and keep watering plain water?

Thanks 😊

 

[ChadWestport]

Are you able to Ph the water yet?