whats the salinity at??
all the rest of the information sounds good though the tank is a little to new for an anemone but i dont think thats the issue. i think your anemone will be fine. they will shrivel to expel waste which also includes purging water and getting cleaner water. mine does it like clockwork even still to this day right as the white lights go down and blues go up he starts. its quite normal. the mouth does look odd in the picture but ive seen many do that before and they were healthy.
another subject to go over is feeding. while under good lights BTA's DO NOT require feedings. however most people do feed them to make them grow faster and bigger. a few options of food to feed them are; squid, oyster, clam, scallop, shrimp, small chunks of fish. whichever you choose make sure you buy fresh. one thing to stay away from is silverslides they have caused problems and even killed anemones due to spoiled fish. just a bad product to feed. i personally rotate oyster and squid i catch most of it myself but i do buy sometimes. fish markets are great and usually much fresher than the grocery store but some places do not have those available so grocery store is the next best thing.. one other thing to look for is that you do not want to feed cooked food only raw. try not to get anything with added perservatives if possible.
