Total newbie here... I got 3 girls last week, different ages but they were all between 6-8 weeks old. The guy I got them from was not feeding them medicated feed. Should I start now? I know that the point of it is to help them develop their little immune systems, so would they still need it, or are they old enough that they should be okay? (I unthinkingly bought unmedicated, but can go and get the medicated stuff today). thanks!