Fin Rot treatment without medication??

I have a fish I believe has fin rot! His pectoral fins got ripped up by a fish that ive gotten rid of months ago. His fins stayed pretty torn up and now It appears to be the beginning of fin rot where the ends have a bit of milky white buildup on the ends. I do not have a hosptial tank so i prefer not to treat the whole tank with medication unless i need to. Will this heal on its own if i keep the water clean?

The affected fish is a Golden Severum in a 55 gallon. I do weekly water changes at 10%-15%. My water parameters are:

Ammonia: 0
Nitrite: 0
Nitrate: 20
pH: 8.0

Ok and im assuming to take carbon out of my filters while using this?

As of tonight i will be on my final dose of API triple sulfa and i don't feel like the milky edges have gone away. Is it possible that it is not fin rot? From what I am observing, the fins are ragged (from his fight which was months ago) and the edges are slightly thicker than the rest of his fin. Is that maybe just the fin growing back? I've heard the fin usually doesnt grow back perfectly. Most pictures I see of fin rot show brown fins and its been awhile that hes had this, so to me they should be brown if the disease was progressing.

Lets see if this works

Thanks to both of you! I will try that and see how it works!