Reef1589 I wish I had more to offer you. I don't. I have seen giganteas in the condition that you are showing, and the prognosis is not good. I don't know why, but these anemones are really fickle when first placed in a tank. If lighting is good, and flow is good, it has to be something in the anemone (bacterial?) or something in the water. I have to say that doing nothing (at this point) will lead you to a dead anemone. I would consider water changes first before I would try treating with anti-bacterial agents (in a separate tank).
Sorry that I don't have more to offer you...