Use Of Protozin Beyond 6 Days

[Bugdozer]

I'm using protozin to treat (possible) ich, and it says "treat on days 1,2,3 and 6." It's day 6 today and there's still at least one spot on my fish. If I want to continue treatment, how often should I dose the tank?

 

[WILDER]

Water change. Run some black carbon for 24 hours.
Water change., Then add the med again.