Withering Seedlings??

I planted some seedlings in a humidity dome about a week ago. They are in a soiless mixture that is maintained at 80-90% humidity and 80-90 degrees. Compact florescent light is timed at 18 light 6 dark. The seedling rapidly shot up and reached about 2.5 inches yesterday. Now today it looks like the leaves are withering and the plant is starting to droop. Im hopeing someone can help me figure out when to transplant the seedling from the humidity dome into a bigger pot under a vegetative light.