See picture. I got this star fish about a month ago. He moves around the tank and goes into the sand. Seems to be doing OK but I'm not sure if he has a sickness/disease or something is nibbling on him. Looks like small chunks of him are gone and the tips of a couple of his tentacles are missing. The only thing in my tank that I could think would take bits out of him are the conches or the hermit crabs. I didn't circle all the white marks on his body. Any insight is appreciate. Thank you.