MBK is love
and welcome to this forum
Looks to me like damage from tearing his body under something heavy but it's a bit hard to judge from pictures alone. Does he have missing scales on more places on his body or only there? Hows his general health and activity? Does he do anything different than before -f.e. always on the hot side while he normally changes between hot and cold, more lethargic, not striking his food as he used to, etc.
There are some bacterial infections (f.e. Salmonella ssp.) that can cause scales to drop, rot, etc, but generally look much more severe than your pictures. See when he sheds if it gets worse or better. If anything, it's best to visit a vet when you see something turn worse over time.
Also hot side can be 86-88 F, and cool around 78-79 F, with a night drop to the mid 70s. 30% RH seems a tad low on those temps you maintain, but shouldn't be too bad (I keep mine at around 30-40%, but at higher temps, and I have more humid places for him to go since I have a planted vivarium). At least this is my experience.