pink belly question

Hi all. I have a question about one of our bp's. He is shedding, it's a bad shed (even with a humidifier to help out) and it looks to me like his belly is burned. It's pink and raw looking. The problem is that I've checked his heat mat and it says 89 degrees. Is there another reason his belly would look raw and irritated? At this point what do I do to make sure he heals well?
thanks for any help you can give me!

post a picture if you can. their bellies do get very pink before they shed, i believe its from increased blood flow for help in separating the old skin from the new skin, but idk for sure. it shouldnt be that pink after he sheds though.