Zoas not opening

[Alejandro Villalpando]

Hey guys I'm new here. I have a zoa frag and only 2 out of 5 heads open up. I noticed there is something brown on the frag.

 

[Tahoe61]

Sorry image is too blue, and algae on glass makes ID difficult. Turn up whites and move plug closer to glass or hold the frag. You already ruled out Apitasia?

 

[resortez]

+1 on switching whites on. Would also help to get numbers & tank mates, from fish to inverts. Any asterina stars or other hitchhikers in the system?