Betta Fish: Is this another case of fin rot?

Hi all, I've owned bettas for a few years now, and unfortunately, the outcome always seems to result in the same. I can't tell if it's fin rot or mechanical damage, but I got my current betta in October this year, and a few weeks ago I started noticing his fins were splitting. Not wanting him to have the same fate as my previous bettas (see pics), I have put him through a treatment regimen that I've listed below. However, it seems like it's made things worse? Now his fins look way more tattered than before, and they definitely look shorter than they were a few weeks ago. I'm on day 9 of treatment, so I'll soon be reducing the salt concentration. Is there something I'm doing wrong here? He's still eating fine and has energy, but so did my previous betta and it died within a year of ownership.

Parameters:

Tank Size: 5 gal tank, first purchased 2022.

Filter: Marina slim filter bio-carb (minimal flow).

Plants/other organisms: None

Water Conditoner: Top Fin Betta Water Conditioner

Temperature: 25 degrees celsius via water heater

Cleaning: 25% water changes weekly

Food: Fluval Bug Bites. 3-4 pieces twice daily.

Other: one dozen small almond leaves, fake plants (silk).

Current treatment (for 10 days):

1 tsp aquarium salt

added one small almond leaf per day

25% daily water changes (and replacing the appropriate amount of salt)

For what it's worth, ChatGPT says this is normal fin regeneration, but I don't buy it as it looks like to me that his fins are getting shorter.