Do you specifically feed them and if so, with what exactly. High protein intake can be an issue but normally only happens in aquariums with fish where the shrimp will often eat the same (protein-rich) food as the fish. Probably not an issue with your aquarium.
What exactly are the GH and KH levels? If these are fine and are not changing much (same with PH) and there is no nitrate or phosphate it could be an issue with missing minerals (especially calcium). You can try adding minerals or mineral-rich food and see if that helps.
Edit: If you have a very “clean” aquarium, meaning almost no algea for the shrimp to feed on this could be the reason for a mineral deficit, coupled with a high protein food source as mentioned above it can lead to molting issues.
Also do you have a heated aquarium? If so then doing a water change with cold water could be an issue as it can induce early molting.
kylerbentley 
Do you specifically feed them and if so, with what exactly. High protein intake can be an issue but normally only happens in aquariums with fish where the shrimp will often eat the same (protein-rich) food as the fish. Probably not an issue with your aquarium.
What exactly are the GH and KH levels? If these are fine and are not changing much (same with PH) and there is no nitrate or phosphate it could be an issue with missing minerals (especially calcium). You can try adding minerals or mineral-rich food and see if that helps.
Edit: If you have a very “clean” aquarium, meaning almost no algea for the shrimp to feed on this could be the reason for a mineral deficit, coupled with a high protein food source as mentioned above it can lead to molting issues.
Also do you have a heated aquarium? If so then doing a water change with cold water could be an issue as it can induce early molting.
What are the gh kh ph levels? What kind of shrimp is it?
Im guessing lack of calcium but it could be disease