What are you feeding it? It ate every day when I had it, I was giving it 1 silverside per day, but once in a while I would neglect a feeding. It also ate chopped up squid & mysis.
Oh, yea I just remembered I had a HELL of a time getting it off, perhaps I stressed it even further. But remember it was a last minute freeby. I hope you nurture it back, keep me informed. Also, you only have that one light fixture, I would try putting it closer to the light, they love the light.
BTW, the lights are sold!