For what it's worth, even my snakes that are from more arid environments (including my Gray-banded Kingsnake) seem to appreciate the option of a humid hide. They may just spend an hour or two a week in it, or they may sit in it for a day or so at a time - usually during a shed cycle. Assuming there isn't any more serious underlying issue here, you might consider providing a humid hide as well as the regular hides.