Brown thing looks like some type of feather duster. If it is, then it's a good thing.
The white thing in all your pictures is aiptasia. Bad thing. Do NOT scrape it off or mechanically remove it as all the little bits will settle elsewhere and make new ones. Either get some "Joe's Juice" and apply as directed, or mix up a paste of kalk and saltwater and apply the paste on top of it. It'll be gone real quick.