Sometimes it best to cover all bases and use maracyn one and two.
See how he goes with the maracyn.
If no improvement in four days get back to the board.
I will get you some info on maracyn.
Maracyn
Manufacturer: Mardel
A broad-spectrum antibiotic for gram-positive bacterial infections. For infections of columnaris (body fungus), fin and tail rot, popeye, gill disease, and secondary infections.
Active ingredient: Erythromycin.
Maracyn–Two
Manufacturer: Mardel
A broad-spectrum antibiotic for internal or external gram negative bacterial infections which can even be absorbed through the skin. Effective treatment of fin and tail rot, popeye, gill disease, dropsy (swollen body, protruding scales), septicemia (bleeding or red streaks on the body), secondary and internal infections. Effective even when fish won't eat.
Active ingredient: Mincycline hydrochlor.