Looks like we are dealing with bacterial infection here, possibly gram-negative bacteria in which case, tetracycline (if pH is no more than 7.6), kanamycin or a combination of Maracyn and Maracyn 2 can be used.
What are your water parameters? What test kit did you use? Tank size? Tankmates? Foods you give to your fish? Maintenance schedule? We need plenty more details here to correct whatever issues may have caused such.