That's my take too...scale rot. It's not so localized as it would be if it were a burn..but spread along the bottom scales as if it spread out.

I would research the causes of scale rot as it is commonly caused by unsanitary conditions.

I have had to treat a minor burn before and the Vet gave me some 1% Silver Sulfadiazine cream. I also picked up some Nolvasan Antiseptic Ointment later to treat the wounds on a rescue...either will work if there has been no infection set in.

I would keep the temps as are and keep the tub SPOTLESS, clean paper EVERYDAY. Fresh water EVERYDAY a lukewarm bath in Chlorhexidine/water solution EVERYDAY and rub either of those ointments on the areas in question daily until the shed.

If no improvement...a VET visit is necessary.

Remember this: I am NOT a Vet..this is only what has worked for me.