Don't FEED. It needs lot of light, but probably now needs to be acclimated to higher light levels.
Feeding can make it worse as it takes a lot of energy for an anemone to digest particles of food. The occasional bits it gets when it's healthy help balance its nutrition, but it really needs good quality water and lots of light.
Those are some of the reasons I preach leaving these creatures in the wild where they live so long we don't know their lifespan.