I just got 3 sunset plattys from the store a week ago 2 male 1 female. The female has been just staying in one place at the too of the tank. She looks fine otherwise. The next day she swam around a little. She keeps doing it. Today she was just laying in a little rock. Like she was right side up not on her side. Is she pregnant. I don't know water info but I completely changed it right before I added them and i put 1 tsp of stress reducer. It's a 20 gal tank. Please help thanks.! 3 new plattys. 1 female is staying either at the top in the corner or In a rock just sitting there for hours everything else seems fine. Is she prego or sick?