Yesterday, I did a 20% water change in a ten gallon tank and noticed that Rachel's (a red and purple betta) body color changed were she had distinct horizontal lines going across her body looking something like a zebra danio. She was behaving normally and did not seemed stressed. Is this common among bettas to exhibit stripes? Here is a picture of her with normal color. If it happens again at the next water change I will try and get a picture! It did not last long before she was full color again. Any ideas?