Brown like stringy stuff on my zoas


Reefing newb
I have had these zoas for about a month now n I just realized that there is a brown like stringy stuff growing on them. Its in a few places n its also on my rock n a couple of my other corals. I have taken a tooth brush to it last night very lightly n when I touched it it shrunk up n its stopping my corals from opening up. Can anyone tell me what it is and how to get rid of it, I would greatly appreciate it. Thanks