has he attempted to go into aestivation? i dust every feed as i was advised to but lightly. i'd maybe feed a more varied diet, try putting some night crawlers, superworms and fish in there, i find my frog to be interested in everything but crickets. btw heat mats won't burn an animal unless they are used incorrectly or fail, if the probe is under the substrate it will control the temp of glass where the animal will burrow down to. i'd clean the substrate more often, once a month max. does the frog appear to show any signs of metabolic bone disease? this could maybe stop him feeding and will need treated mostlikely by oral or soaks if he ain't for feeding