Betta Fish: New fish owner help

I noticed his tail is fraying. It was not like this when I took a photo of him 3-4 days ago. Is this fin rot? I’m worried I was feeding too much, I was doing flakes and when I vacuumed during water changes there is lots of debris and algae is growing in the tank super fast… I just bought pellets to regulate how much I’m feeding and will do a 50% water
Change tomorrow and then maybe 20% for a few days after that and am switching to pellets. Any other recommendations? I want him to be healthy and for his tail to not be frayed 🙁 how long will it take to heal?