IMO death of an anemone officially begins when some of the flesh (any of it, tentacles/body/foot) begins to decay. It's almost always the beginning of the end though; very few recover.
Flesh stated to decay earlier today - Moved it to a small 10 gal quarantine tank - Foot starting to disintegrate...
I have two pistol shrimps that I can only see at night (mostly hiding in the live rock) and a peppermint shrimp - Everything else in the tank is doing great:
A mated false percula pair (confused as their nest is gone)
Bicolor Angel
Small Yellow Tang
Yellow Watchman Goby
2 Orange Firefish
3 Blue-Green Chromis
One manadrin
A few gazillions copepods and amphipods
A mic of soft and LPS corals that are fully open
A few SPS (that came with my intiial live rock) and only open late before the lights turn off
Tank is 75 with 260 watts Sunpaq lights
Water chemistry was good two days ago (have yet to test since anemone started dying)
Any clue?
That's what I was going to sugest. Try adding a littel Lugo's solution. A couple of drops. Also, how fast is the water moving in the tank? If it is really cruzing, that could also make it unhappy, they don't like high flow.