Banana Purple Punch Auto - FastBuds

I don't think that is mold. i'd use a real pesticide instead of some home remedy concoction. Pyrethrines kill on contact and biodegrade quickly. This too will cause some minor symptoms on the plant. The home remedy appeals to some people, but more often than not it's a urban myth or ineffective nonsense. Spraying random shit on the plant has more risks than benefits. I'd have to look it up, but if potash can traverse the stomata, you may have caused some nutrient lockout or burn. Those darker spots look like a P-deficiency symptom, which is not locked out by K but could be coincidental timing with your actions and unrelated 2nd issue. check ingredients of the neem oil. If it does not have 'azardirechtin' (definitely misspelled) it is not much of a deterrent to pests. "clarified' neem oil doesn't do much of anything. don't leave dead foliage around - keep the area clean. Rotting organic material is a vector for pests. Use Bti pre-emptively to kill pests whose reproduction cycle invovles larva in the soil. You often get this shit in the bag from the store you bought the substrate from, unfortunately.

looks more like necrotizing leaf tissue. I think something in that mix is not great for the plant and causing it to die. You will want to keep air movement up as well as that high RH in the dark phase can lead to fungal growth. You can spray with lights on if they are dimmed way down. but not if they are at full or moderate intensity. Neem has been getting a lot of bad rep lately for its issues with humans and how a lot of places have banned it on any crop that is consumed by humans. Mostly its active ingredient. there are many options out there for treating pests. I would look into some of them as a one stop kill option. Neem stinks as well and does not kill but fucks with the pests reproductive system, not a fan of it.