Scarlett Red cleaning or eating dying firefish?

I have a firefish who suddenly plopped onto the sand and can't get up. It has been lying on its side a bit, not looking good, still with life in it though. The scarlett skunk cleaner shrimp went over and started pecking away. It's impossible to tell whether it was cleaning the fish of parasites or cleaning the fish of its remaining life and protein filled existence. Was wondering what some of you think. I separated the pack and got the firefish in a net. I'll probably take him out and put him in an isolated 5 G until we can see what is wrong. Happened right out of the blue, no warning signs. He had a nice helping of good frozen mysis shrimp the day before and seemed happy.