I had a the same issue with my candino after I got him. I did daily 20% betadine 80% water wipedowns until his next shed. After he shed his belly was nice and clean, no more discoloration. What substrate are you using?
Burns, what heating system are you using. I had this same problem last year when I was using heat pads with aquariums. My females belly is still "scared" from the burns to this day. Whats your heat. If its a heat pad but lots more bedding on and get a different heating system.