Large water changes with ro
water will get things in order. Do not try to feed the anemone. Consuming large chunks of food can be stressful to anemone and result in more energy being expended trying to consume it than what it will get out of it. These anemone will get all they need out of the light source above your tank as long as it is an intense light.
Clownfish can also be stressful on anemone. The symbiotic relationship isn't always the best for them. Clowns can be very rough on them and if they aren't established anemone, it can even lead to them being picked on to death by a clownfish.