That anemone was not happy. The tentacles pinched off not due to fish biting it or anemone waging war but due to his unhappiness. You need to find our what it is and correct it. It seem that you successfully did it. In general, try to keep things as stable as much as you can.
There are certain things that is particularly bad for anemone (and other sensitive animals). Poor water condition is one. Top off weekly is another one. Most successful long term reefers top off continuously or at least daily. Do you add two parts calcium supplements? If you add Kalk too fast or alkalinity too fast which cause spike in pH, can also do this. This, spike in pH, cause a lot of stress for the animal. High temperature spike during the day also. As LTA get larger, they also want deeper sand. Consider this and consider adding more sand to the area where the anemone is at.
Good luck with your anemone. Post a picture.
