Strange flatworm living on Rhodactis mushrooms

[jdmneon]

These worms live in/around my purple hairy Rhodactis Mushrooms, they blend in so much that they aren't really noticeable at all, I thought they were sweeper tentacles or something at first but there are dozens and dozens on a single mushroom, they don't seem to live on any of my other coral I only began to notice because one of the mushrooms didn't look so great, most of these things are about 1/2 cm long

I know the picture isn't great but it's hard to get anything decent

these worms swim in an undulating manner that reminds me of a nudibranch, they don't bother me but I'm worried they are parasites, I have had these mushrooms for about a week

any advice would be greatly appreciated

 

[jdmneon]

can anyone speak to this?

 

[Dave & Monica]

Really need a better pic, can be a nudi. Hard to tell.