Keep an eye on him
but to be honest he's just being a lazy betta like they can
Have you changed his water yet?
I have him in a community tank and I changed the water yesterday, I only did what I usually did so I don't see that being the problem. None of the other fish have ever shown any signs of aggression towards him or from him to the others. I have noticed a slight swelling increase, I'll try the pea treatment again tonight, I don't have another tank except a 2.5Gallon tank, would it be cruel to isolate him in there so I can make sure he's not eating the other fishes food?
I feed him a variety, flake/pellets/algae wafers, cycle through them per night.