Fwiw, all shrimp shed their shells from time to time. The exoskeleton can't stretch so it has to crack and allow the growing animal to get out and expand in size. Moulting is what we call that, and it's very common to think you have a dead shrimp, when you have a moulted exoskeleton in fact.
The same is true of any animals with exoskeletons that are growing.
Do leave them in the tank, shrimp eat them to recycle the calcium content.