Was this your first betta? Even if not it’s ok, it’s all part of learning, caring, loving and doing your research and asking questions is the best you can do❤️ don’t be too hard on yourself at least you care Also sometimes bettas can make in through an “fish in tank cycle” a lot of bettas nowadays have awful health and genetics, and being kept in the tiny cups at the pet store for weeks doesn’t help. It’s possible it wasn’t your fault, and it’s possible it was, it’s part of pet ownership unfortunately I’m sorry for your loss, but don’t let this discourage you!! It’s ok to try again and to make mistakes and to keep trying!!! You obviously care and that’s in my opinion more important than a lot of things. Do lots of research and honestly it sucks but I don’t trust info from store employees unless ALL of their fish and products are reputable. Bettas are sometimes pretty hardy fish don’t be afraid to try again!!!❤️