My parameters are all fine, corals, fish all fine except him. My guess is he tried to sift through gravel and sucked up something too large for him to sift? He was fine just a couple days ago. Now he basically just lays in a cave all day not moving unless something spooks him out, in which case he awkwardly swims out by flapping his front fins and dragging his tail until he finds another cave to lay in. Occasionally he seems to do that wide gasping, gagging looking thing with his mouth. He stopped eating, sifting, and cleaning out his cave too. Not sure what to do.