You are already using the best med, i would keep an eye on water stats as it will wipe the bacterial colony out.
Tetracycline
Manufacturer: Aquatronics
A broad-spectrum antibiotic used in the treatment of gram-positive and some gram-negative bacterial infections. For infections of fin and tail rot, frayed fins, popeye, inflamed gills, mouth and body open sores/ulcers, livebearer disease, dropsy, Columnaris, and secondary infections such as fungal. Specific for livebearers and goldfish. Aerate the aquarium well when using. Useful for the control of some common bacterial diseases, including Aeromonias and Pseudomonas Genera and the Mysobacterial group.
Tetracycline
Manufacturer: Aquatronics
A broad-spectrum antibiotic used in the treatment of gram-positive and some gram-negative bacterial infections. For infections of fin and tail rot, frayed fins, popeye, inflamed gills, mouth and body open sores/ulcers, livebearer disease, dropsy, Columnaris, and secondary infections such as fungal. Specific for livebearers and goldfish. Aerate the aquarium well when using. Useful for the control of some common bacterial diseases, including Aeromonias and Pseudomonas Genera and the Mysobacterial group.