Moulting is when a shrimp, crab or other invertebrate sheds its old exoskeleton to grow a larger one — the discarded empty shell is a healthy sign, not a death.
New keepers often panic at what looks like a dead shrimp on the sand; it's usually just the cast-off shell. Inverts are vulnerable and hide while their new shell hardens, and they need stable calcium and magnesium to moult properly.