Did you ever work out the ventilation? You will probably need to provide more information regarding the soil composition, watering schedule, etc. Are those clay pots or plastic?

Either way, it looks like the soil may be a bit too rich for the young plants. If you don't have proper drainage, you could be seeing the beginnings of root rot. If you are overwatering, especially if they are clay pots... that will harm the plant.

But yeah... you probably need to include more specifics about your situation. If you want an accurate diagnosis from someone... fill this out:
http://boards.cannabis.com/plant-pro...anted-one.html