Have you tried keeping them in smaller setups? I've never kept this species before. Is that nighttime temp in the appropriate range? I'm not saying that it isn't, it just seems that 80's at night is rather warm, especially for a small snake.

Have you tried offering frogs, skinks, other prey items etc? If it were my snake I'd move it to smaller cage, and probably deli-cup the animal with a live pink overnight and see if it helps.