Yucky, have you tested all possible water parameters? Everything, Phosphates? Nitrates? etc.... Are you dosing to much Iodide/Iodine? Are you using Tap Water? If so you better get to your LFS, since you are in Seattle I know Saltwater City carries a PolyFilter Pad which is $9.99 that will take out any impurities in the water. I've used them my whole time in this hobby. They work very well.
Also, the coral may be having problems from shipping issues. Maybe it was miss treated in the shipment and didn't show any signs of death until recently? There could be many possibilties, but first check all the water parameters.
How good is your lighting setup? Etc... Need to know all that.
I checked my water last week and earlier today, but everything seemed to test out fine. This coral started going downhill when the heat started in Seattle (I don't have air-conditioning in my home). My lightning is 2 VHO's and a MH.
This was the center piece in my tank, but now it looks like it going away...... :-(