I'm new here, but I find something very different with betas.
After reading a lot of books on them before I bought one and right after; it's best to reconstruct what sort of food they would have in the wild. Feeding them pellets is fine, but vary the food with some blood worms or brine shrimp. Also, I feed my fish about every 3 to 4 days, sometimes every day, sometimes every other day. Try to reenact the amount he would get in the wild, varying it like this makes him less dependable on the food and healthier in the long run.