Something is wrong with my mealworms colony..

[Kheyg Kharra]

I was trying to raise a colony of mealworms, but got an issue that most of the beetles just start laying on their backs and helplessly squirm around. If I try to flip them over they stumble and roll over again. I thought that it's their food that causes it, but I'm feeding them the same kind of vegetables and fruits I feed my cockroaches, and they seem to be fine. What can cause this?

 

[Introvertebrate]

They may be the world's clumsiest beetles, but eventually they get themselves right-side-up again. I put a piece of egg crate in there and they seem to be all over it.