I have mold on the back wall of my TBHs, and on some of the yet unused bars. I live in Southern California, and it's usually very dry during the day but we're having foggy nights and mornings right now (our June Gloom.) I made the TBHs from old toy chests I bought and the lids do not fit tightly, allowing for some top ventilation. The entrances are three 1" holes I drilled in the front toward the bottom of the space. The bottom of the hives are sealed. I do not use follower boards.

So, too much ventilation or not enough?? What's the best way to reduce this condensation/dampness in our very dry climate??