Hello, got this tiny cluster of Zoas from the LFS (for free) almost 3 weeks ago. Some of the polyps have never opened before (not even at the LFS), and the ones that do don't open fully. Occasionally I'd see some dark brown stuff on top of the polyps that takes a while to go away. Can still see some of the brown stuff in the picture. Any idea what's wrong? Is my coral sick or something? My tank is a 5G with 18W Power Compacts by the way.