The Internet said that fish lopsidedness is often a bladder gas issue caused by over-feeding. The human felt guilty because he sure had been over-feeding lately, to compensate for the cold weather. Maybe fish don't naturally overeat to put on a layer of blubber in winter like the humans do. So, Munchung underwent a fishy fast for two days, before slowly being given small amounts of food again. A few days later, and she was right-side-up again. She now swims happily and normally, to the relief of all. Happy fish.