A error in foundation/spacer people?

Humans had virus, white cells, and overpopulation. Spacer worlds(Aurora, Solaria, and Melpomenia) had no white cells, controlled population and was phobic of other races(humans and aliens). By the time of trantor, did they change it back n to overpopulation and all was out-and-about as if the non-white cells thing cease?

Sorry if its messy, I try to say/text it the best I can