Quarantine as quickly as possible and Google the net for fish diseases. If you do not have a quarantine tank set up, get one of those one or two gallon terrariums that most LFS's have, treat the water you add with a conditioner and put your fish in. Add the medication you need along with a fungal salt and make daily partial water changes, but keep the medicine ratio up with the water you replace. Now I know that a lot of fish will be stressed out by this type of treatment, no heater and no filter but it is absolutely necessary to prevent the spread of the ailment to other tank mates. I have treated an Oto this way and they are extremely sensible to water changes. Even if you only put your fish in for two days, at least you have done something to start off the healing process!
Good luck!