Thats not heater burnmarks. They get these marks and you can se symmetri of the marks. Black rays get them to but its more prominent on brown rays. Dont know what it is but its not anything to be worried about. Their skin is like sandpaper and think of these marks as a rougher sandpaper instead of the fine. My motoromale has marks like these to and he is perfecly healthy same goes with my bd x henlei female.
