Maracyn/Maracyn 2 Treatment Question

I have a Betta that I am pretty sure has a bacterial infection. I have been treating him with a combo of Maracyn/Maracyn 2 for the recommended 5 days.

He is improving, but is still not 100%. I believe that I should treat him for another 5 days. My question is:

Should I do a partial water change before I start another 5 day regime? And if so, how much of a water change should I do?

OK, to answer my own question and for all of you out there wondering-

I called the company and they said to do a 50% water change before I started the second round.