Well bleaching and RTN are two different things.
Bleaching itself can be caused by a number of different things, however bleaching can be recovered from.
IME once an acro starts RTN, it is extremely difficult and unlikely to save. I have fragged up coral colonies that started RTN, and maybe saved a frag or two from them, but it seems when they start to go like that, it is difficult to turn around.
Bleaching on the other hand can usually be stopped and the coral can regain it's health by reducing the stressors on the coral, ensuring good water quality and flow, perhaps limiting or lowering the amount of light. Although that makes it sound much easier than it seems.
