You can try a couple of things: put the superworms in a wider, shallower dish (make the bedding thinner), leave the top off to give better air flow, and avoid using super wet food stuffs - stick with drier veggies, no fruit. Use a dry bedding, too, like oats.
Once they get established, they are hard to get rid of. Happily superworms are cheap. Toss em and start over.