Whats up with my cleaner shrimp?

[Nano]

Ok yea another problem I know... but seriously here it is. I just got a cleaner shrimp about 3 weeks ago and he always had a great appetite and very active always cleanin. Yesterday and today he seems to be twitching and laying on his back at times for up to five minutes sometimes, then suddenly he's back to business climbing rocks and doing "shrimp" stuff. My parameters are spot on except my calcium being slightly low at 360. No changes to anything in the tank or new diets or anything. Everyone else is fine corals are huge and opened nicely fish are getting along "swimmingly" but he is "tweeking out" anyone know what the problem is here? Is this out of the ordinary? He just molted yesterday morning so other then that its just the behaviour that is concerning me.