I have several hundred dubias. I noticed 2 days ago a nymph on its side. When I picked it up it was dead. Same thing yesterday only this one was near dead. They were fairly large nymphs but not the same age. The first one was about the size of a dime and the second was about the size of a quarter. I did notice on the second nymph that it was arching its back (like we bend over with a tummy ache). And one of its legs was eaten or something hollowed out, only visible underneath. Should I be worried? What could it be and what can I do to fix this problem?