Betta fin rot question

I'm treating my betta for fin rot. He seems perkier and all after the
first round, but does anyone have any clues as to what I should look
for in terms of doing another round of Maracyn II or not? His fins
deteriorated so slowly, I missed that it was even happening for a few
weeks, so I really don't know what to look for. Do you think I should
just do another 5 days just to be sure? Any clues appreciated.

dragon