Yellow Leather Eating Nudibranch

[baller71ss]

So my yellow leather hasn't been looking so hot the last few days. Which isn't real surprising because it seemed like for every day it had full polyp extension, it had a day of little to no extension. I decided to check it out, and found a patch on it's underside that seemed to be deteriorating. Then it moved. Then it kept moving. Got some tweezers, and this is what I found...

Now the real question is....How shall I kill it? I'm open to suggestions...