Sorry can't really see much of anything with the photo.. I can tell he's very clamped.
Tetra Easy Balance messes with ph.. why are you using it? I would definitely discontinue.
When you do water changes are you also cleaning the gravel with vac/siphon or stir/dip method? You really only need one 50% a week if it is fully cycled. If you're unsure you shouls test.. imho any time you don't do weekly 100% changes you should have a drops kit for ammonia, nitrite and nitrate on hand to be able to monitor levels.
He's acting like parasites or some kind or ammonia burns. He shouldn't have any ammonia issues with that water change routine.