i have a 4 foot marine tank with 2 seahorses,2 star fish,2 hermit crabs,cleaner shrimp,sand sifter,gobie,scooter benny,mushrooms, sponges,a crab that eats hair elgae and soft coarls. today i found that one of my star fish has lost its legs. doe's anyone know what would of done this to my star fish