Royal Gramma dying

[sarzeff]

My Royal Gramma is dying and I'm not sure why. My other fish looks fine and the water all tests well. She had a bit of ick but was treated and seemed to be doing great, then a few days ago she started hiding again and now is pretty much dead this morning. It doesn't look like ick at all has come back...no white spots. Any ideas? She was possibly older when I bought her as our LFS doesn't have a high turnover rate and she was hiding in the reef tank. She's a big fish and was big since I got her so I suspected she may have been older.