Odd blue hippo tang behavior

Okay, at first I thought maybe they were "scratching" because of ich.  But paying closer attention, I noticed that they were taking turns are "hosting" the green star polyps.  The one with the dorsal fins laying down will spend about 30 seconds at a time in the GSP like so...

Then not ten seconds after this one left, the other one would come in and do the same thing, but not as long.  Is there any reason why this one would have the dorsal fins erect?

I don't think they are breeding since I believe they are still too young, roughly 5 months or so.  But they will rest in the GSP and I've never noticed it before.

 

I sat there and watched them for about ten minutes scratching my head, then looking all in the GSP to see if they were leaving anything behind or what.    
Another thing, I had my anemone in a 10 gal trying to split it by water changes.  I didn't have enough time to take care of another tank after a few weeks, so I put it back in main tank where it was hoping it would stay put.  Well, it didn't and just last week after a month of not knowing if it was alive or dead in the rock work.   I found it in my sump in my refuge alive and well.