I'm pretty new to anemones, too, and I've just had a BTA for one month now. It seems to be doing very well, but I do notice that it gets stressed and closes sometimes when a shrimp bothers it. My peppermint mainly only bothers it when it sees that the anemone has food. (But I've learned to be sure to feed some meat to the general population in the tank before feeding the anemone). But the other day, I was just lucky enough to get a glimpse of a pistol shrimp (who The in my rockwork) picking on the anemone when the light went off. There wasn't much I could do, so I let nature take its course. Eventually the shrimp left the anemone alone and he opened back up... not a much as usual, but enough to satisfy me. The next day, he was nice and full. I'm hoping the clowns I have in QT will decide to hang out with the anemone and help keep the shrimp away.
Also, my anemone's mouth has opened and release brown stringy stuff, which some will tell you is a bad thing (meaning it's expelling the beneficial algae). But I feel like that might be okay for an adapting anemone to do it a little. Mine did this a couple weeks ago, but his mouth tightened back up afterwards and I haven't seen it since. I've had a rock flower anemone for over a year now, and it also did this a time or two during the first couple of months. Does your anemone's mouth stay tight when it's not expelling or eating? That would be a good sign. I understand that if it stays loose, that is an indication that something in wrong.