I can’t figure out what’s going on with my Betta Fish

Hello I’m having a problem with my betta this is the second dose today of using seachem kanaplex I thought his fin were looking a bit better but now they both look horribly ripped he’s in 3.7 tank with a low flow sponge filter and a heater at 82-degrees I did a 75% water change today I do believe he is a fin nipper and I don’t know how else to treat his fins or stress he’s swimming great and eating like normal please help my little guy mr. Nippy I have a video with a much better quality of what he looks like . Thank you !