If he's eating/defecating/shedding regularly then i wouldn't be worried about it. Just like people, corns are different from one to the next on what they "like". I have a female who never ever is on her warm side. Normally this might be a cause for concern (maybe her warm side is too warm? she's sick?), but the temps are fine and she's 100% healthy. She eats, sheds, poops, and breeds like clockwork. She's just different in what her ideal temps are. So if all appears normal I wouldn't worry too much about it.