Burn on belly?

[toripyth]

While holding my brazilian rainbow today I noticed a couple darkened spots on his underbelly that almost looked.. charred. Upon further inspection it looked as if part of the scales had actually chipped away. Can anyone tell me what this is from?
He does have a heating mat located underneath his hide box. I use reptibark as a substrate and have a lot of natural wood in his terrarium. Also, I have a fogger that runs all night long and leave it off during the day to help prevent mold growth. I'm not sure if any of this info would help but I included it just incase.
Thanks!

For some reason when I try to include the URL for the pictures I get a message saying 'post denied'? I'm not sure how I'll be able to add pictures.