Sorry to hear of your recent disease outbreak. I once lost 13 bettas over a three week period, because I bought an infected betta from a local fish store, and back then I did not sterilize the turkey baster that I used to siphon out the tanks and containers. I unknowingly spread the columnaris bacteria to every betta I had. Columnaris is nasty and can kill a seemingly healthy betta in 24 hours, showing up in different ways (finrot, gill fuzz, body fuzz, bubbled lip).
I would suggest a combination of anti-fungal and anti-bacterial medications with some melafix. Then you would need to sterilize your tanks, nets and siphons, even the tanks of the healthy fish. My mistake was not sterilizing everything immediately. Once I sterilized everything, the outbreak stopped, but I lost 70 to 80% of my bettas. It was a tough lesson to learn.