Fungal outbreak? That's impossible. Fungal infections do not establish themselves as outbreaks since they need an open wound to be able to do that unless all your fish suddenly injured themselves for various reasons that led to broken skin everywhere.
Your situation sounded more of bacterial infection than fungal infection. Fungal infections are hard to come by and many bacterial infections have been misdiagnosed as fungal infections.
Triple sulfa is an antibiotic. Almost all antibiotics have adverse effects on beneficial bacteria which is why it is always a good idea to have backup established filter medias in case you have to treat your main tank with antibiotics.
Recommended dosage. 250 mg per 10 gallons every 24 hours with a 25% water change before each treatment. Treat for a minimum of 10 days.
Did you quarantine your new fish? If not, why? I believe it would be more prudent if you conducted quarantine procedures to every new fish you get regardless of the circumstances. It is not that complicated. All it takes is a barebottom tank/tub (preferably 10g) operated with a heater and sponge filter. You can then administer 0.3% solution of salt and praziquantel to destroy possible flukes, aeromonas and internal parasites, all of which are common ailments found in the aquarium industry.
