To be honest, without seeing exactly what the anemone is doing, I can't really tell you much. Try to get pics of the anemone as best you can when its behavior changes. I am not being rude by any means, but do you know what a gaping anemone mouth looks like? Without closer pics, there is no way to ascertain that--especially if you've never seen what a gaping or healthy mouth looks like. I hesitate to say much else except that a gaping mouth is indeed a bad sign. If something is done quickly to help the anemone, you may be able to save it, but it usually doesn't bode well.