He looks dead i would take him out..they are hard to keep on youtube fish of hex leaves his back glass dirty because its the only place his starfish seems to eat from so they're very picky as to their food source and water quality
Hmmm then it might've been a PH, salinity or dissolved oxygen swing? they are very sensitive creatures... and you should never handle them(out of water) or take them out of the water at all apparently...