my anemone is dying...its sad...

[Jaws]

One of my RBTA is doing the same. He did really well for a long time and then started moving around all over my tank. He'd hang out behind the rocks for weeks not getting any light and now his tentacles are almost completely shriveled. He stopped eating on a regular basis as well. Do anemones have a lifespan because this was a fairly old anemone that has split numerous times. His brother still lives on very well in the same tank.