My betta has been acting strange lately. A lot of hanging out at the bottom of the tank, his body leaning sort of sideways against the gravel rocks. His mouth also looks a little strange...sort of swollen. He's in a two gallon unfiltered, heated tank. I do weekly water changes with aged, treated water. I've had him exactly a year now. My last two bettas lived between 1 and 2 years. Do you think he's just old, or could he have something I can treat? He's still eating and swimming around some. His water temperature has remained fairly constant, so I don't think it's heat related. Any suggestions?