I bought a mated pair of true percs from Aquatek on Sat. PM. Both are enjoying their new anemone! They run their tanks at 1.023 so this should not be an issue. I had them keep the fish for a week to ensure all was OK.
I think most of us have had the sudden death situation, I just put it down to a weak or stressed fish. I had a yellow tang that slowly died from not eating. Nothing would entice him to eat, and eventually the lawnmower blenny started picking on him for no apparent reason. In the end I had to put him out of his misery as he was in a hell of a state. I have had a new yellow in the tank for over 2 months, no problems…. go figure.

Hope you find out what the problem is.

- Tim