I have a 20g high with 3 dwarf gourami, 10 neon tetras, 3 platys, 2 female one male. Like 2 days ago my platy was fine and swimming and eating. But yesterday it didn't eat at all, it's mainly staying at one spot on the gravel. It's dorsal fin is up so I don't think it's stress. It's didn't swimming touch but it does a little. And I tried to force feed it today but when my hand got close the others swam away fast but he just stayed they're swimming away slowly. It kind of looked like it lost strength.