You cant have too much humidity, its essential to have neer 100% humidity at the surface for good pinning, the worst that can happen from high humidity is that you get mycelium growing on the stems of your shrooms. This of coarse is still good to eat. Alot of people here just to be safe, disgard a small portion of the stem at the bottom that may have peices of verm in it.

Your over reacting becuase the desired humidity is 95% . It's a good idea to fan every day or so to let out C02 build up but other than that, you should be happy with the results. Fat-asses may be a growth trait or just luck of the draw. "Normal" mushrooms are no different then fat-asses other then looks. Personally, I like fat-asses :-)

-Hightiemsreader