I don't see why it wouldn't work on mushy's, we zapped a big green button polyp and it died just like the aiptasia did; We also zapped some green star polyps that were encrouching on other corals. Although it did take a bit more zapping do to the larger size of the polyps. Mushrooms and all soft corals would respond the same i would think, i wonder if you didn't zap yours long enough Chris? I will post some more videos of other corals getting zapped on thursday-when my camera man is here
Cheers Ronnie