magnifica anemone Deflated... HELP?

[MitchM]

If you've had this anemone for 3 years and this is unusual behaviour for it, I would check over your water parameters.
Otherwise, I consider it normal behaviour, as long as it doesn't last too long, like a few days. Do you have any shrimps? I've seen them tear into an anemone to get food that it's recently consumed.