Or mist him in his cage periodically to keep the humidity up for a while & see if it improves. I'd also recommend adding a "humid hide", one with saturated sphagnum
moss in it (& use a large enough & new plastic food container with a snap off top- cut a 'doorway' in the top- you don't want a regular hide that's open on the bottom,
so as to contain all that extra moisture from the regular substrate). Many kinds of snakes enjoy having a humid hide, once you show them the door-way, the damp
aroma of moss seems to entice them right in & they'll feel snug inside while having a "spa day".