HELP! Doomed or panicking?

[FrankV]

Hi there
Background
First timer with possibly a very dumb question.
Outside pot grow, soil/coir/perlite roughly equally. Been flushing for a week, on about week 11 now (label fell off). This one stunted and I think this was due to a bad re-pottting, or its just the lowryder being particularity low.

It's either a Lowryder by Vision seeds or a Fast Buds Gelato (never using eco-labels in the wind again). If anyone with a good eye can tell me which they would also win my undying admiration. Whichever one this is, the other is doing very well indeed.
Issue
Severe burn(?) on the leaf of an otherwise healthy plant, its been raining here so they've been inside a greenhouse for a few days with less circulation than I'd like.
It may just be time to harvest soon an this is normal, but I've seen yellowing on a few of the others (auto Frisian dew) and wonder if its related or possibly bud rot.
It looks relatively healthy and if its just a case of leaving it or cutting the leaf off I don't know.

Honestly I've been a bit stumped by this, any help greatly appreciated. Any glaring things I'm doing wrong also feel free to point out, I'm as amateur as they come.

[duckman]

hard to say, FrankV ... first thing I would say is you've got a ways to go before harvest, based on those pistils...might be too wet and sign of a root problem. if it's just a handful of leaves and isn't spreading quickly I guess I'd just monitor her for now while it dries out a bit. good luck!

[FrankV]

Thanks, I'll keep an eye on things and honestly just pray for good weather. I'm surprised they've taken so long to develop tbh. Do you know if its normal for autoflowers to just take a while if conditions aren't ideal? This has been a VERY steep learning curve looooool

[JohnEmad]

Hi FrankV,
Breeders times frames are based on near perfect conditions.
I have had autos go 10 or even 20 days longer so just have to watch the pistils and then the trichomes closer to be sure.
Looks good for a 1st grow.

[FrankV]

That makes me feel a WHOLE lot better, I had wondered about that and am pretty relieved its not a major screw up by me

[alltatup]

That's not a "severely burned leaf": it's dead. You have other leaves around the one that's dying that are showing signs of deficiency, the veins on the lower fan leaves are turning yellowish brown..

I'm betting it's evidence of pH problems which ultimately cause nutrient lockout. https://www.growweedeasy.com/flushing-sick-cannabis

[Rwise]

Looks like mine did after I burned them with an overdose of nutes.

[SoOrbudgal]

I would say water/nute overload.

[FrankV]

Thank you everyone, I think aggregating your responses it is likely to be a pH issue, as this is the element I'm controlling the least strongly. Hadn't realised how major it was, I've been going easy on the nutes recently but did use fish tank water for one feeding which rapidly changed the pH. I think this rapid change is likely the cause. Having measured its coming out of my tap at like 7.5, so potentially will start adjusting with some sulphuric acid I have handy (very very carefully), had been trying to avoid that as its kinda scary to introduce anything like that to the plants.

[JohnEmad]

I agree with alltatup.
Sulphuric acid seems way overboard and may cause quick and severe ph swings.
I would suggest getting something from a grow shop or reputable supplier like ph down or ph up.
Sulphuric could result in you making multiple batches of water or nutrient solution to get it right.
Once you have adjusted something down too far it is not recommended to use another agent to bring it up.

[Rwise]

If one uses Sulfur, and it is in all soil (though not enuf in mine), than add water, the water and sulfur make sulfuric acid. The sulfuric acid is a PH down.

[Obi-Wan]

I’m with Rwise on this one, Sulfuric acid or Phosphoric acid, the plant uses both bonded minerals so it’s not about what the acid is bonded to it’s about the concentration of the acid and how we dilute it. Everything that brings the pH down is an acid of some sort, it’s the concentration that makes the poison.

[F10werChyld]

If you don't have a botanical pH down additive, use white vinegar to get your pH into the proper range. I wouldn't try sulphuric acid

[JohnEmad]

Vinegar is fine but it doesn't keep the ph stable for long.
How do I know that? lol.

[Rwise]

IMHO vinegar is a waist of time.

[FrankV]

Thanks everyone I have not you'll be glad to hear used it, it's actually aquarium pH down so 9% acid but still, probably not best. The ones currently in the final stages of flowering I'm just gonna hope for the best on and the others i will try and use a dilution of vinegar. I have a pH test kit so don't mind spending a bit of time adjusting.

I also have scaled back the nutes, was definitely overdoing it on that. I'm now dealing with a fair number of bugs which is pretty annoying but potentially the vinegar may scare them off? They do seem to be doing okay and are very close to harvest. Luckily the weather has really picked up in the last few days so both me and them are loving it

[Rwise]

Absolutely nothing wrong with using sulfuric acid to PH with, it is created in the soil anyway.

[JohnEmad]

I wonder how much sulphuric acid is created in most soils as you say Rwise?
Would think the amount would be extremely small. Adding from liquid Sulphuric acid solution seems dicey to me. OK if you dilute it down big time I suppose.
I had at one time worked day to day with large amounts of sulphuric, Hydrochloric, and even near 100% caustic soda. All dangerous stuff if not handled correctly.