What kind of lighting did you have over it before? If it was a lot weaker, then the anemone isn't used to the new light. Imaging after after winter going out for a full day in spring you would get burnt really bad. But by the end of the summer, you don't get burnt as badly by being out in the sun for the same amount of time. Our skin adapts to the new lighting just like the anemone needs to. I would suggest cutting the lights down to a few hours then gradually over a period of a few weeks slowly increasing the amount of time they are on.