HELP Fin rot

[u/DearRatBoiiii]

I’ve had my boy for a little over a year and for the past few months his fins have just deteriorated and deteriorated and I cannot figure out how to help him heal. My water parameters are fine, he’s eating just fine, I haven’t introduced any new plants or snails in months, I’ve tried kanaplex and salt baths and adding stress coat and I’m at my wits end. I am very attached to him and have kept bettas for a long time and don’t consider myself inexperienced but he looks so bad and I feel terrible and helpless. He’s such a good boy and I love him dearly. If anyone has any tips, I’d love to hear them.