Betta Fish: My betta Kumo just randomly passed away :(

My beautiful boy Kumo just randomly died after I came back from a 3 day trip to the coast. There were no signs of his health decreasing apart from the day I left there was a weird scratch on his side.

I honestly thought nothing of it as he was still swimming around happily and eating fine. I did also notice that he was struggling to jump out of the water and accurately get the food on my finger when I was doing tricks with him but I think thay might just be because the top of the water was a little bit cloudy as I filled the tank up over the filter line meaning there was no flow up at the top which created it.

I don't think it was due to the water condition as when I tested it everything was normal and my shrimp and snails were all healthy.

I sort of hope it was just bad genetics and not my fault because I tried my best to keep him happy and healthy. Anyway I'm so upset I have lost him and I do want to make sure my tank is perfect before I do get another fish, maybe leave it for a few months or so 🙁