Unless your fish has a rampant infection (causing fin rot) Prime and regular water changes ought to be enough. :)
I actually like Stress Coat for new fish. I have seen it make a difference in fish changed to new tanks. It's not 'essential' (prime is, for me!) but I find it a decent product for fish's first few days, or after a shock of some kind. Not so much for diseases.
Try Prime + very clean water for a couple weeks. New fin growth looks clear or pale.
If that doesn't work, or the fins start looking very dark and/or raggedy at the ends, that's when I'd look at meds for bacterial issues.
Mild cases can sometimes respond to a few days' treatment with Aquarium salt. But, as I've had fin rot progress incredibly quickly and be a symptom of a much worse illness that salt doesn't help, these days I prefer clean water -- then meds. No messing about, I hit the germs hard before they get worse and observe good quarantine practises (learned the hard way..). This seems to work okay for me and my fish.