I think the dr is saying that the aiptasia are on other rocks, but wants to know if anything on this rock is bad as well (?)
The yellow spherical shaped thing is likely a sponge (although there are some tunicates that can look a lot like sponges.) Being that it is small, I wouldn't think it would cause a problem.
The translucent white tubular things (they are small, but have an obvious excurrent hole, usually the point that sticks out the farthest into the water) are rather common hitchhiking sponges that will survive in systems that have enough nutrients in them.
The numerous white string-like things that seem to cover the rock... Those I am not sure of. I have certain rocks that they seem to be on (mostly where there is low flow) and others where they are absent. I don't think I have seen whatever it is specifically mentioned anywhere.