Take it down while you got something left. I just finished my first grow. I had plant that had buds start to turn brown.... It's just the first sign of what is probably a terminal illness of your plant.
Of the 8 plants I had going, all outdoor, I had to fight bud rot on 7 of them. Probably because my location was chosen because it got direct sun all day. It happened, though, to be in a very low lying area with a creek flowing about 10 feet away. In late summer and early fall we get fog most every night. I think this is why I had the bud rot issues.
Anyway, all but one of my girls were sativa dominate hybrids. The quickest to develope was a girl that I started from seed in mid July. She was only about 4.5 feet tall when she got chopped down. I was really Looking forward to her. I expected to be chopping her down last week September or first week October. On September 14 my brother was over and wanted to see them. I noticed some brown spots on two of the colas of this girl, and on several of the buds on the side branches.
I assumed it was bud rot, but this being my first time growing marijuana I figured I would let it ride a bit to learn for the benefit of this sick girls sisters.
Three days later I went to check on them for the first time since I noticed the bud rot. The experiment ended right then and I chopped her down. After she was dried I had three ounces of ugly bud. A significant portion of what didn't rot looked ugly because it was close to The rotting buds. So of my three ounces of bud, probably an ounce was ugly.
There were 42 grams of rotten buds. Useless! I wouldn't smoke them. I didn't even attempt to sell them because it doesn't even look like weed, it doesn't smell like weed, it could make someone sick for all I know and it doesn't even look like it contains THC. It didn't even make it to hash material pile.
So, because I waited three days after I noticed it, I got about 1.5 ounces of smokable buds. I got about the same amount of buds that one could have probably smoked or sold, but I added it to my hash pile.
If I had cut it down the day I noticed it, I would have probably harvested 5 ounces instead of 3.
If the plant had no problems, or if I kept on top of it like it did with this girls sisters, and the buds were able to fully ripen, I would have probably 7 ounces because they really fatten up in those last two weeks.
Immediately I started throughly examining the buds on my other girls. Although I lost some weight from cutting out hunks of buds that started to exhibit signs of rot, it was a minuscule loss compared to what WILL happen to your plants if you don't take care of the bud rot as soon as you notice it.
If you see tiny brown areas on your buds cut them out. If you see large patches of brown, unless its just on one branch, your best off to just take the whole plant. A little bag of bud is better than a big empty bag.