I have a pincushion urchin, two actually, and one of them seems to be dying. He’s larger than our other one and he’s been dropping spines randomly since day one. He does eat and move around, but I’ve recently noticed a small hole in the very top of his shell (is shell the right word? It’s just at the top of him) and a small black spot on his side. He also started pulling his spines flat at the top near the hole, but today he had a lot pulled flat (pictures for reference that I just took of him)