Dot dash Butterflies killed by Bubble Tip Anemone

[Portsmouth Reef]

I had 2 Dot dash Butterflyfish which appeared to be a male female pair. They got on well for a week, one was cleaning the other, and they swam together most of the time. Then a week later they were both found at seperate times under the Anemone,
unable to right themselves. One recovered briefly, then swam round the back and hasnt reemerged in 3 days. The other one I pulled out 3days ago. I cant believe that these large beautiful fish could succumb as easily as they did. has anyone any experience of this?