RTN or hopefully something else HELP

[Aquattro]

Originally Posted by reefermadness

Also I've never had a acro RTN over redbugs.

Not RTN, but PQTN for sure. I've lost whole colonies, once they started, they were gone in days.
But probably not what happened here. Just a set of parameters that were likely too different to it's source tank. Too much light typically would cause bleaching, too little and it goes brown. PO4 is a bit high, so that could affect it.
Differing flow patterns, often bigger pieces are more affected. The fragging process probably wasn't the cause, I got a 1/3 of a tabling piece 2 months ago that we just cut into three. All three are doing fine in three different tanks.
Unfortunately in the world of SPS, sometimes this happens. If you keep those pieces that you cut off, you got lucky.