I noticed that just now when my male platy was swimming away, he did like a flip. His body was upside down for a moment. So, he might have a swim bladder issue. Most of the time he swims normally but I've noticed occasionally he will flip upside down briefly. No idea why. It's not the filter, the filter is low flow. The only thing I can think of is maybe something I fed him? I did give them kale yesterday. I hope he'll be okay. I didn't expect to have more issues so soon after I've gotten maintenance and water quality under control.