looks like its been starving to death. probably a bad purchase. looses spines when injured or dying. if ur finding it upside down somethings turning it over or its to weak to hold on itself and attacking its mouth trying to eat it. if you have a nori sheet put it on top of a piece. if doesnt eat it fairly quickly its most likely dying. they constantly eat and unless you have tons of algae they easily starve, and in those pics you posted I see very little for it to eat in your system too.