I agree with DarkMoon, it looks like he is coloring up. Marble Bettas sometimes change color a lot over their lifetimes. There don't seem to be any black edges so I also don't think he has fin rot.
I would stop the meds and aq salt, give him a rest. If there's anything I learned on this forum it's that clean water often does the trick, and that medicine should be a last resort unless the case is drastic. Give him fresh clean conditioned water for a little while and see if he doesn't perk up and his fins look better.
If his fins don't get better, you can try an aq salt treatment (just salt, no meds). It will probably be easiest to do this in a 1 gal QT tank or container that you can float in the 14 to maintain temperature. For ten days change water every day and prepare the fresh water with 1tsp aq salt (per gal if you use a bigger container). Stop the salt after ten days but keep up daily water changes in QT until he's looking better.
He may be biting them or tearing them on something in the tank. I don't really see the problem in those pics so it is hard to tell what's going on. Make sure all your decorations pass the pantyhose test and aren't likely to tear his fins.
Good luck! He is a cutie.