Overwatering perhaps? do you have any drainage holes in that cup?
I don’t have any holes…should I add some?
yes you always want the water you put into any plant to drain out of the bottom. It could cause your roots to rot, develop mold or fungus, and that’s just the start of those issues.
That may not even be your problem, I would copy and paste the support ticket and fill out the proper information and a professional could help you better than I could.
Soil could be too hot too.
too much fertilizer? Not enough light? Poor seed…it happens