Hello gjjdemarco,
Even thought pictures would be helpful, from your description of water level and where you notice it growing, I don't believe it's mold. I would guess it's algae. Algae is a micro flora (tiny plants). First it won't really hurt your plants, it can use dissolved oxygen in the water the plants need, but you would need a lot of it to make any difference. Algae needs 3 things to grow. 1. water/moisture. 2. food (like
nutrients in the
nutrient solution). 3. Light (that's why it's growing on top of the growing media). You need water and nutrients for the plants to grow. But you can adjust the water height so the very top of the growing media stays dry while still keeping the root ball moist. Also you can just cover the top of the growing media with cardboard, Styrofoam, or plastic lid to block light. If it doesn't go away (die of) shortly after you block the light from it, then it's not algae and some type of fungi (mold is a type of fungi).
P.S.
Humidity is good for plants even up to 80%-85%, however without good air circulation it can easily cause fungal spores to germinate in areas that stay wet all the time. Usually this happens on the plants foliage, and the fungi feeds on the plants leaves. Good air circulation will also be beneficial to help pollinate plants like peppers and tomato's. An oscillating fan is a good idea, but I would let it run 24/7 and make sure it covers the entire plant area, or get enough fans so it does.