SPS turning white.

[Chowder]

You can try that but it also can be water quality or stability. In my tank I am battling Alk swings. I loose a piece about once every two weeks. Starts the same way as yours. Ive have stopped a few pieces from fully dieing but don't know what I did other then get the Alk back to around 9 DKH. The best thing you can do for SPS is keep your water as stable as you can.

Chris