I recently purchased 2 sally lightfoots for my 75 gallon tank. Coral and fish combo. But one has lost a pincher and the other was torn apart. I do have a large green brittle star. But I have never seen it go after anything. The wife feeds it by hand. Help in whats hurting the crabs? I also have 2 blue legged hermit crabs. Have been told they will tear up other critters.