Fin rot in betta?

I got my beta a few months ago and he seemed completely fine until about a week ago when I saw his find turning white. I’ve been treating him with aquarium salt and stress coat + but he seems to be getting worse every day. Parts of his fins are falling off, but he still seems very lively and normal,

Hi and welcome to the forum

Have you tested the water quality?
What is the ammonia, nitrite, nitrate and pH of the water?

Is there a filter on the tank?
Is the filter run continuously?

How often do you do water changes and how much water do you change?
Is the new water free of chlorine/ chloramine before adding it to the tank?
Do you gravel clean the substrate when doing water changes?

Can you post another picture?
Use the flash on the camera and have the room light and tank light on, and open the curtain. The previous image is quite dark and doesn't show much.

What are your parameters, and how old is the betta?