I think it might be too late.This is my first og kush I have ever seen with Botrytis. If I were u I would very carefully trim off every bit of brown or dead growth in that area off as soon as possible as this shit spreads fast. Also do not touch any other buds while u do this as this will spread contamination. Bold mold is from high humidity or wet conditions. Indoors keep humidity at around 50rh in bloom and right below 70rh in veg . Outdoors choose a mold resistant strain.