Galaxy
Fish Fanatic
Rather than the long reply by my learned friend above my advice would be simple. Try increasing the salt content of your water slightly. I have ten mollies and on two seaprate occasions two different black female mollies started acting strangely. Each time the fish started staying close to the bottom and not really swimming round with the others. staying in the one corner of the tank for hours on end. At feeding time she would only slowly respond and take only a little flake as it sank.
Both times this happened I did a partial water change increasing the amount of salt in the new water. Within a few hours I noticed the fish perking up. I know that this will be more difficult for you to control as you have other community fish besides mollies who may not like the salt. Maybe you should remove several of the mollies together into a more brackish tank for a few days. Salt can help cleanse the fish of a lingering illness which otherwise would be difficult to treat or even diagnose. If the fish perks up you could try returning them to the main tank.
I guess this turned into quite a lengthy reply after all. Oops!
Both times this happened I did a partial water change increasing the amount of salt in the new water. Within a few hours I noticed the fish perking up. I know that this will be more difficult for you to control as you have other community fish besides mollies who may not like the salt. Maybe you should remove several of the mollies together into a more brackish tank for a few days. Salt can help cleanse the fish of a lingering illness which otherwise would be difficult to treat or even diagnose. If the fish perks up you could try returning them to the main tank.
I guess this turned into quite a lengthy reply after all. Oops!