I agree with all I read above: air movement and venting. It sounds like most of your crops are cold-tolerant, so daily venting may help a little.
I've read that underwatering is a good idea in wintertime hoop tunnels.
One way to mitigate the effect of soggy soilless mixes and humid or stagnant air is to provide a dry surface on each pot. Think of it as "mini-mulching". I like pine bark chunks around a half-inch for small pots, or up to one inch for larger pots. Water runs right around them. Then air circulates enough to dry the bark chunks. This may help keep soil-dwelling fungus and mold away from the plant stems.
You'll still have to keep the air moving and less humid, or mold spores will start living on leaves.
And bottom watering is sure to keep the root zone moist with less humidity than surface misting will. The soil surface needs to dry out often. Only the roots need water.
P.S. When water evaporates from moist soil, the evaporation removes a lot of heat from the soil. If the humid air then condenses on the plastic greenhouse wall, it exports that heat right out of the greenhouse. Dryer air will probably also translate into warmer air.
