I dunno. They look like BTA to me (admittedly not an expert). Could you quarantine for a while and see if they grow into BTA or if they spread like Mojano? Or, as dbl suggested, get the yumas off the rock and up the rock into QT and see what happens.
I'm not as paranoid about hitchhikers as a lot of folks.
[probably because I haven't gotten any of the really bad hitchhikers yet]
Ok, so we had just gotten that rock last night in a trade, it was a huge slab. I just spent a good 45 minutes breaking it all up, gluing the yumas to plugs, and setting aside 3 of the questionable anemones. I've put them in a little container in our biocube to see what becomes of them. If they grow, then I've got three GBTAs to go with my 3 RBTAs! If they multiply, then they go in the trash.