Chances are fixing the cage temperatures will fix your feeding problem. It is hard to suggest other things to do at this point. This time of year is their breeding season so they tend to go off feed anyway. They can go a year without eating. The best way to tell if they are in trouble or not is to get a scale and weigh him. (a cheap $15 kitchen scale will do)
I was told hot rocks would kill a snake and not to use them... This UTH gets warm but not hot at all, it said it was specifically designed for glass enclosures and I have a layer of reptile-carpet substrate below my newspaper...