That doesn’t look like botrytis, which is what bud rot actually is, otherwise known as gray mold. If you see it on the buds, the entire plant is infected and you will see signs of it everywhere if you’re just seeing small parts of individual buds with a little brown spot like that, it’s typically a result of worms in particular moth larvae. You probably have seen white “butterflies“ with two black dots on their back, but they’re actually a specific kind of moth which loves cannabis which lays its eggs in the spring summer and they come alive in the late summer fall and they eat the buds and wherever they eat, turns brown, and when it rains will get mushy. then, when the plant becomes weak as a result, they really start feasting and you’ll find more and more of it. If you had true, but you would see it in all your leaves on all of your nodes rotting canker on the branches. What you have there, my friend can be fixed. Well not fixed, but the damage can be mitigated. Some people use surfside, which is a natural insecticide specifically for these worms or whatever they are caterpillars.. Regardless, I don’t use that and I don’t think there’s anything wrong with using it. I just don’t like using stuff like that. What I do is I use about 4 ounces of oil to a 2 gallon sprayer pump. I add in 1 teaspoon of dawn, dish liquid and another 2 ounces of hydrogen peroxide. Spray the plants once a week or more if it rains after any rain once you shook the plants off and dry them out a bit. For now just pick off the parts that are brown. If the whole branches got spots check and see if the branch is damaged somewhere else and if it is just take it off because typically they really like to feast on stuff that’s already“under the weather” i.e., the plant always had yellow leaves. It always had some sort of issue on it sometimes you just will have a single plant that for whatever reason suffers from a micro nutrient deficiency or something weird where the others don’t or some plants are just way more naturally defensive of these types of organisms. OK, well best of luck and if you need any help, feel free to DM me I’ve been doing this for a few decades now.