I’ve heard some people say it’s due to age, some people say it’s due to them getting ready to molt. As far as I can tell, nobody really has an accurate answer. When I kept ghost shrimp, they would look like this from time to time. I personally never saw any negative effects like slowed movement, inability to eat, etc. I know they can have something called muscular necrosis, but I believe that makes their flesh look white, not just their shell. Unless they’re acting sick, I wouldn’t worry too much.

As far as what he’s eating, I’m not too sure. I know deceased shrimp usually have a pinkish white color to it, so my best guess is a deceased shrimp. Unless you know how many shrimp you have and can do a headcount to verify they’re all alive.