Zoos dying???

[blackjacktang]

I have a zoos. It is like one side of it is dying and the other is fine. Like on the dying side, the polyps have not opened in about 3-4 days. The good side has been open and looking healthy. Why is one side not opening?
Here is a diagram of it.
Key
Blue=good area
Red=not opening area

 

[michaeltx]

could be bacteria or nudi or a fish in the tank.
what are your water parameters and fish stocked in the tank?
Mike