Thank you all for the discussion- I was looking for everyone's experiences. It is interesting, this morning I couldn't hardly find one. I thought the sixline was doing an amazing job, he looks nice and fat. This afternoon I see a bunch. Not a big deal- they aren't affecting any of my corals yet. They are localized on just a single rock.
I'm not afraid to use the Flatworm Exit, I will dose it if I need to- but I'm going to just let this go and observe what happens. I suspect like most things, this is just a phase that will pass.
Let me know if you disagree.