Variety is best for health, and mealworms have the risk of causing blockage in the intestinal tract, due to their hard skin.
If you don't want to harm him, get some variety, and replace meal worms with super worms (Zophobos morio), they are softer skinned.
Some other care that is important to keep him from harm is:
1. What is your supplement and vitamin schedule?
2. What types of basking light bulb and UVB bulb do you use, it will help us determine if you are creating MDB and other health risks.
3. How often do you offer water, and how?
These are amazing creatures, but without proper husbandry, they perish quickly.
CHEERS!
Nick