Bubble Tip Anemone Advice Needed

Friends,
My green bubble tip anemone has a habit of shrinking... or should I say deflating. When it deflates it deflates almost entirely. It does it almost daily but always seems to come back. The first time I noticed this was when I did my first water change and I thought it was due to the shock. But it has consistently been doing every day since, always inflating itself back to its normal size. Is this normal? Do bubble tips have a tendency to do this or am I doing something it doesnt like?

Amphiprion,
I've had it about 3 weeks and I didnt notice it until the second week when I did the 13 percent water change. All parameters are a go: ph 8.4, trates 0, trites 0, ammonia 0, salinity 1.024, temp 78.

I'll have to admit though that I havent been testing for alkalinity. I have no tester for it but I'm going out tomorrow to get one. My worry is that low alkalinity is the reason for my brain and my torch coral not doing so great.

Thanks for the reply, its a bit comforting to hear that its normal, albeit not daily.