Dominique Welcome to this exciting movement Dom! Your English is fine.
The beetles eat the same thing as mealworms, except they usually eat much less than the mealworms.
Carrots are definitely one of their favorite and least likely to spoil/mold.
If you want more pupae, feed them regularly (every other day).
Also, it's natural for some worms, pupae, and beetles to die off. You will eventually grow a more stable colony as you find out their favorite feeding schedule, type of food, and more!