Looking at the the straight head on photo dosent seem bloated at all to me.Blue diamonds can have a tendency to to crap a brick when then go,2-3 times bigger then other fish.I think you need to up your wc's in general,but for now atleast do as many as you can,Id say at least 3 times a week 50% or more if you can and see if that gets his appetite back.In my experience when the fish is bloated you can see it in their bellys and sometimes it affects thier swimming.