Betta fin rot medication?

[alli789]

What's a good next step to take if aquarium salt doesn't work to treat fin rot in a betta? It seems like so many medications have mixed reviews and risks. Is there a fairly safe one that I should try?
His fin rot was on just his tail, but I'm starting to notice dark spots and small splits on the back of his anal fin. The small amount of new growth he had seems to be gone and he still has dark edges on his fin tears. I finished the salt treatment several weeks ago and filtered all the salt out of the tank over the course of two weeks, per Colin's instructions. The only current treatment is indian almond leaves.
Can I do a second salt treatment at this point or is it too soon? I've been trying to eliminate reasons that the fin rot might've not gone away, like stress, so I've added red root floaters to reduce nitrates and I switched to a gentler filter (using cycled media). Since his stress should be down, maybe the salt would work better this time? I've also been looking at Maracyn 2. Anyone have experience with it?

Tank is cycled and stable, 10 gallons, heated at 79 degrees. Been doing two water changes per week since finishing the salt treatment, one 10% and one 25-30%.

 

[Colin_T]

broad spectrum medication containing methylene blue and formaldehyde or acriflavine.

is the tank clean?
is there any ammonia or nitrite in the water?

 

[alli789]

broad spectrum medication containing methylene blue and formaldehyde or acriflavine.

is the tank clean?
is there any ammonia or nitrite in the water?

Yes, the tank is clean. I've been gravel vacuuming at least some gravel with every water change and it was kept very waste free during the salt treatment. I've been rinsing the filter media in tank water when dirty, usually once every 1-2 weeks. There's no ammonia or nitrite and nitrates are kept below 20ppm, usually between 10-15.

Forgot to mention that I'm fairly sure his fin rot is bacterial, not fungal, I don't see any holes and he has those dark edges on the torn/split parts.