There's an interesting article about RTN i found awhile ago. RTN is pretty much like looking at a dead guy and saying "he died fast". How did he die? that's totally different. Corals get sicks much the same as people, lots of different diseases caused by many different things. We all have slightly different parameters in water, dosing with different chemicals etc, so saying one thing causes it doesn't seem to be effective. There's very few things known about RTN, but we do know that stressed corals are more likely to get affected. Corals can regrow, even RTN'd corals, so according to this the best thing for RTN corals is high flow, stable parameters and fragging if possible.
Ineteresting article though, i'm sure some of you have found it:
http://www.reefs.org/library/talklog/eb_jl_111598.html