Anemones generally don't like change very much - even if it's change in a better direction.
Your lad looks a bit bleached - might not be a horrible idea to offer him some small meals of the same sorts of frozen foods you give your fish until his zooxanthellae repopulate.
My anemone shrinks up at night all the time and comes back when the lights come on. Also anemones should be added to a mature tank that has gone through all the ugly stages already. Like maybe 8 months to a year in