I've got the LG styrobator everyone loves to hate. Usually run 50-70%, not bad I guess. But I ALWAYS get a spike of about 103 near the end of the second week and have to adjust the temp. Then it ALWAYS goes cool after most of the chicks are hatched, in the brooder, and I'm just waiting on the stragglers. So I have to turn it back up.
An I crazy for believing this is because the chicks are putting off their own heat?
No you're not crazy for that
You're not using ventholes to control humidity are you?
Nope. Everyone told me not to. But I haven't hatched in THIS THREAD yet.