Do I feed enough?

[anglfish]

Yesterday one of my Nassarius snails munched away on my Lettuce Nudibranch.

By the time I was able to scare the snail away, the Nudibranch had a big piece (half its size) missing. I don't know whether it is going to make it.

I noticed before that the Nassarius snails always come out when i feet Mysis or other meats, but to attack a live and healthy Nudibranch?? is that common or is that a sign that I don't feed enough.