I had the same problem with a couple of my own bettas in the past. With both I eventually decided it was dropsy, treated them with Maracyn-II and fed them frozen bloodworms every other feeding. They both recovered fully in about five days.
Loman, will bettas really eat peas? I've fed peas to goldfish before(who will devour them) but never to a betta. I know they're primarily insectivores by nature, so I never thought to feed them any veggies.
