I read that the incubator temperature may need to be fiddled with as the chicks develop because they're putting off their own heat.
Mine is doing the same...even with my house heated it dropped the last two nights to 97° and went up to 102° during the afternoon.I'm afraid to walk away and have it go above 102°
I just had to tweak my bators last night. They were toasty. Going to keep it lower the rest of the time.