my female betta is in a 1 gallon vase (no plants, just her and her marbles) and for some reason tonight, she's decided to swim to the bottom and just lie there with her fins clamped. when i walk by, she'll swim up and unclamp her fins. i walk away, and she swims back down to the exact same spot. i just did a water change today, but i did the same water change i do every week. what do you think is the matter?