I'm wondering as well if a good soak might be in order in case that dry poor look to his scales might be a lot of retained shed from previous poor husbandry. Rather than have a drinking dish big enough to soak in all the time just pop him in a small plastic container with tepid (not cold or hot water) just up to his back but not over - not deep enough he must swim. Give him an hour then let him slither through a rough damp facecloth or inside a damp pillowcase. Might help if you think it could be some old shed stuck on there.