apparently, superworms/king mealworms don't really have a high nutritional content, due to the fact that the majority of distributors rarely feed/gutload these feeder insects. Also, the high chitin/shell content of the "worm" is relatively high, so the risk of impaction is there. Try silkworms-soft bodied caterpillars, high in nutrition.

if all else fails, gutload those superworms and hope for the best!

good luck