I think my anemone is sick

[Angel]

For the last week or so it has been having what looks to be the inside of its stomach coming out of his mouth a little bit. its not the usual deflating and spitting up of dark brown goo that it usually does, it is a white layer of tissue. Today it started to look really bad. Im not sure what to do. I did just add a bubble wall at the back of the tank, and the light seems to be fine for tha other one that is in there and thriving. I just got it about three weeks ago