Interesting....
This is a 10gal divided tank...with 5 males correct....
Filter, live plants, how much and how often are the water changes, water temp, additives used, any tank mates like shrimp or snails, appetite, treatment tried, do you have a water test kit to test water prams....tell me about your source water......tap, well, filtered...etc......
Behavior..any changes or changes in appetite....