I'd be so bold as to suggest adding a macrolide antibiotic like erythromycin to shotgun at dropsy or popeye if they happen. I've been successful in turning both diseases around exclusively with erythromycin (where doxy, tmp sulfa, and kanamycin didn't work)
Also do you have an aminoglycoside? Kanamycin/gentamycin/amikacin are my favorites and my go to drugs when i have an external bacterial infection.