Is it powdery mildew or Botrytis (bud mold) ?
Powdery (white) mildew can be controlled with Serenade.

Botrytis (grey mold) can be treated with Trichoderma or Gliocladium roseum in the early stages. Evaporated sulfer will help alot but applying it would be tricky.
Treat mold like a contageous virus, it will destroy your crop if left unchecked. Cut it out at least one or two inches below the mold with shears dipped in rubbing alcohol.
Got any pics of the damage?
With 9 weeks of flowering seems like they should be ready. Only nearly pure Sativa strains need more than that especially if the temps are getting cold.