I need help! My most prized blue halfmoon is losing his tail fins! Its like they are slowly disintegrating and I've tried all sorts or treatments to get his fins to improve and heal with zero improvement. I lost a Silver Dragon Scale with similar symptoms, and I don't want to have to lose my Big...

For any who do not know who Spartan is: he is 2.5 years old, 3 in February. I got him when he was an itty bitty dull orange approximately 6 month old betta. When he was 2 he survived a mystery poisoning, and since then has gone strong. Recently I found out his dark blue spot was really a tumor...