will my leeks be ok?

hi all, i sowd my leeks in a tray(the DD way) a month ago in seed compost ,watered them and theyve germinated ok. i then put them in a cold greenhouse.i checked on them a week later and the compost had dried out and cracked so i watered again.i looked at them today and there is carpet of fine green mould!! on the compost.is this normal? or are they in danger!.ive quickly sown some "back ups"in some  moist multipurpose compost this time and not watered them.reasurance please.

phew!!