That plant is way too deep in the pot.
The soil does not appear to have any lighteners.
Re-pot into good soil and raise the level of the base of the plant up to no more than 1 inch below the rim of the pot for better air flow. That is a classic suffocation symptom.
BTW the leaves can still be green with fert burn, just the tips get scorchy.
stinkyattic Reviewed by stinkyattic on . Possible Humidity Problem The plant is abot 5 weeks old now. Im still using 20/4 light schedule. The reason the plant is so small is Nute burn when it was young and incorrect light spectrum for 3 weeks. The problem is that some of the leaves are drying up.So bad that they are crumbling away.The leaves are still green so its not nute burn. I dont know what my humidity is but i reckon the air is too dry. Rating: 5