My platty, guppy and angelfish all have bloated abdomens, which got worse after a water change. They swim and eat fine, and fins fly high. No problems. They just look bloated in the belly. It's not dropsy or swim bladder - I've seen both of those before and that's not what I see now. What do I do? My water tests are fine, except that, as usual, my sourcewater is hard and high in phosphate.