I'm sorry. These fish need multiple meals a day. Very messy eaters. I wish I could tell you if he was getting enough food or not. They are a thin fish to begin with a very high metabolism.I fed two cubes of frozen every night, about an hour or two after feeding pellets to the rest of the tank so the other fish wouldn't be as aggressive eating. I also made sure to not touch the big aiptasia in my overflow so he always had babies to eat, which he was always picking at my rocks for. Maybe that wasn’t enough for him...
If you do try a cbb again, offer 3 to 5 feedings. I know it sounds like a lot. It's how I keep mine chunky.