Not sure what this is...

[Pilot]

...so maybe someone on here can help. I have an sh pot full of Onc twinkles and one species Onc that is used in the twinkle lines.


But what is going on with the leaves? I have it in sh, the affected leaves are both old and new, though more of the old ones are affected than the new ones, and I have it on a heating mat. Roots and bulbs actively growing and I water weakly weekly with a 20, 10, 20 grow more urea free fertilizer, with Epsom salt added, just a pinch to a gallon bucket, and they're grown under lights, at least until it's warm enough to move them outside.

Any ideas?