Time will tell if it is going to die or not. The most important thing you can do for this anemone is to get the water conditions as close to perfect as you can. You bought the anemone already comprimised and now it is in conditions that are less than ideal (or at least were at the time you posted "nitrates 40-50" and temp "76"). H. magnifica generally do not rebound as easily as a BTA, but they can rebound. Feeding is not an option right now as the anemone is not healthy enough for it, but maybe it will come back.