Thanks so much both of you.
I haven't missed any major tank maintenance. Still doing regular water changes and substrate changes, plus spot cleaning and stirring the substrate. However, I DID recently change substrate types (by accident).
I saw some of what I thought was his usual finely ground coco fiber on sale at an online store and bought 12 bricks of it. When it showed up to my door, it turned out to be almost like compressed coco bark with some fiber mixed in. He's only been tong-feeding, so there's not an impaction risk. Although since the stuff is rougher than what he's used to it's easy to see how it could be irritating his skin
His dechlorinator hasn't changed, and I never handle him unless I'm giving him a soak or absolutely HAVE to take him out of his tank.
He hasn't been bloated, eats like a hog, and has always been lazy. He does perk up anytime he sees food though.

Think I might need to just toss the new substrate and get him back on his old stuff.