Sorry for your loss...
I know this probably isn't going to help you any, but I have a feeling I'm going through a similar experience right now. Mystic has never seemed right since I brought him home almost two months ago. He has that persistent fin rot going on. I'll get it slowed with salt and clear with an antibiotic. He'll be showing signs of no infection and regrowth after a week on antibiotics full dosage. Two days back in his tank his fins just start deteriorating again. This time they had white stuff hanging off of them yesterday and today it looks like he mauled his poor anal fin. I got him back on the meds I'm going to try 2 rounds of the maracyn plus this time.