I got three red people eater heads about two months ago and recently two heads have died and the other has not come out for few days. Water parameters are good and all other corals are fine so kinda stumped on why these guys died. I did notice two little unkown crabs roaming on the rocks which are probably not reef safe...havent been able to catch them. I dont think this is the reason but this is first time I have had people eaters so wondering if anyone had any ideas. I have moved them to other locations in tank but no love........they were to nice why they lasted

, hopefully this one head comes back.
Thanks
Brandon