Yup, you're right about the bubble algae
First pic looks like Acans to me. They look like they've receeded in the past and some are coming back. See the dead skeletal structures ? When they're super happy you won't see any of the structure at all
Second pic I don't have a good idea, so I'll leave it to someone else
Third pic could be a monti cap, but it's a bit blurry for my bad eyesight
Fourth pic is a branching frogspawn, and is a gorgeous critter btw. Keep it away from others it can sting when it sends out sweeper tentacles