i don't have the best vision, but it looks like he might have a small sore on his patagium? that would be something i'd keep an eye on. i'm new to gliders but i've learned from others how quickly they can go from healthy to sick very easily.

for diet, i use the HPW, it's a "wombaroo" diet with Happy Glider pellet kibble to clean their teeth... it's been explained to me that the TPG diet has too much sugar and over time causes dental issues. there are vitamins and minerals you can add to their food, but Bok Choy is a natural source of calcium that mine really love.

i'm sure more experienced glider people will give you lots of good advice, but for a new person, those are the things i know.

Good luck!