I can't be certain. Came across a few threads with people experiencing something similar. Not sure if they're eating zoas, or it's just irritating them to a point of them just dying/melting.
I think thats whats happening. Irritation. I just install my frag tank n got no fish there so mayb they are reproducing too fast?? And need some kind of pods eating fish?? Mandarin or a wrasse??
Found same nudis on polyps in my sis in law tank. I can say I definitely took 2 off of 2 seperate zoos. I can also say tons of zoos that were perfect are gone. Unfortunately I'm not there enough to know for sure but imo it's them.