So from what I have read, the Tropic Marin Pro Coral Cure kills the adults but not the eggs. Potassium permanganate kills both the adults and the eggs but it can be difficult to get ahold of. However, you need to be able to remove all of the montipora from your tank in order for this to work as you can't treat the whole tank with these chemicals.
I had them a few months ago, I removed every M. capricornis I had. I had one crappy digitata growing in the back forty that I couldn't reach and appeared unaffected. I also had a prized M. undata out the front that appeared unaffected and as it was out front I kept an eagle eye on it. I ended up treating all of my caps with potassium permanganate which did a bang up job. I then couldn't get the darned things back into position and ended up fragging them (note: I didn't keep my tank monti free for x number of weeks as you're "supposed to", I just chucked them back in). I now have only a couple of chunks of cap in my tank which are unmounted and land in all sorts of weird unhealthy places. I keep making less room for them as I stuff other corals into my tank.
Anyway, I'm not sure what else you can use to treat the eggs as they are difficult to scrape off (if you do indeed have eggs).
Ok so on to natural predators. Well while I was trying to take a photo of my nudis I had carefully placed into photographing position, my tailspot wrasse swooped in and ate them. I think this contributed to not having an intense outbreak as there was plenty of capricornis' to go around. There have also been reports that yellow wrasses and other Halichoeres wrasses eating them. I have no doubt that a 6 line would likely eat them as well, but haven't read any information on this. One difficulty in keeping your tank nudi free with the wrasse would be the scrolling of the coral. I found most of my nudi infestation was within the scrolls where my lardbutt wrasse couldn't get into (his girth is rather substantial). A smaller/younger/less well fed wrasse
might have been able to get in there and get them (a theory anyways).
Good luck!