Wet seedlings

I have a small greenhouse which I heat at about 75% during day, and 65-70% at night. My heater has a low speed fan which is on all the time, the exhaust fan goes on periodically when the temp. Reaches a certain point. I open the intake vents, about 3x/day my question is however, why are my seedlings retaining a lot of water, almost to the point where they are wet,not moist. I water very little. I have not put the circulating fan on much because it cools the greenhouse down too much. Does anyone have any thoughts on this. I'm concerned because I'm getting a lot of damping off. I have both bottom watered, as well as just misting the seedlings to moistend them, but still damping off occurs. Thank you