jpc i agree with bang (as usual).
when you first place an invert in your tank they will usually shed within the first 2 -6 days because of the change in water parameters from where they came. also, younger inverts are growing faster to get to adult size, so they will molt more often. that one looks pretty big already, so when it is ready it will molt. you also dont have to see the molt. if you notice you dont see the shrimp for three days, then it probably happened behind the scenes.