Watch the raised scales as that can be a sign of mites. When a snake has mites these nasty little horrors go under the scales and raise them. If he is on Aspen, seeing mites would be quite difficult that's why I have all my snakes (except my Pueblan Milksnake who's on Aspen) on white kitchen paper towel. Anything nasty can be spotted immediately. If he does have mites, then they can lead to the snake being anaemic because they suck the snake's blood. It would also make him very uncomfortable. Mites are about the size of a full stop, about 3 times the size after they've had a feed of the snake's blood. Easily dealt with especially in the USA as you can get Provent-a-Mite. We can't get that here in the UK (yet).
Taking him to the vet is the best way and I hope he gets healthy soon which I'm sure he will with such a caring new owner.