Well, it depends on whether you were buying freeze-dried, frozen, or live bloodworms. Each comes with their own set of problems. Some bettas get constipated after eating the freeze-dried ones (especially if they're fed FD bloodworms as a main part of their diet), and live bloodworms always have the risk of parasites coming in with them. Frozen would probably be your best bet, but they don't keep for long, and if you only have a few bettas to feed, it'll be a massive waste of money. Personally, I've never had issues with feeding my fish freeze-dried bloodworms, but then again, I only give the bloodworms twice a week in very small quantities as a treat.
There's a big argument of sorts when it comes to feeding bettas peas. Some say that it works for them, but personally, I'm in the camp that says it's not good for them. It irritates their digestive system enough to expel any blockage, but ruins their delicate stomachs bit by bit.