Fin rot? Yish! My Juju had that too. I used some kind of homeopathic stuff with tee tree oil in it that I got will the used tank. Can't remember if I still have it though. He also went blind the day he died. He always ran into things. I had him for almost a year. You haven't had him that long, right?
I've only had him a few days. I started treating him last night and he was a little more sickly looking then. He seems to be a bit better now, but I still have to watch him and treat him.
Update: Feiro's eyes have cleared. It seemed that he was probably dealing with a bit of eye cloud as well, but it's gone. Now he can see, eat, and see what he's eating. It'll take time to see if the treatment helps his fins though. I hope it does.
Well, all looks well again. Feiro seems to be over his fin rot now he's just got to grow the fin back that he lost. I made a post for this other betta I got, but I've only gotten one suggestion so far for a name. So here he is. Another beautiful betta if I do say so myself.