For 6 weeks, they seem extremely stunted. My guess is that your light is too close or you're overwatering. That little dot could come with either of these but it's nothing to worry about in of itself. I'd focus on their dwarfing.
Could be anything. Get a fan or light breeze on them. Just enough for the leaves to move slightly in the wind to prevent anything sitting and taking hold. Hopefully that will solve it.