I don’t really see anymore tubes on the rocks, so could just be an old something. If there are more tubes attached to the rocks, those are what needs to be looked at. Now would be a good time to scrub the rock with a stiff bustle brush to remove if you have more.
If not, just keep a close watch for tubes popping up. Vermatids are not harmful per say. They can just grow quick, annoy corals, and the annoyance is what hurts the corals. It causes them to retract their polyps for way to long sometimes.
Again, just keep an eye out and research vermatids a little, so you know what you are looking for. There are a few types of them, so keep that in mind.