My first SW death (xenia)

[Whiskey]

I've just transfered the contents of my ~5 month established 40 breeder into a new-to-me custom 65 gallon. So far I've misplaced a monti cap (anyone got a frag of a red one I could buy?) and some xenia I've got on a rock has started to die. I'm wondering what the procedure is for a dead/dying softie. Do I cut the bulk of it off near the rock and take it out of the tank to try and preserve water quality or do I leave it in the tank and let it decay naturally?