During the final stage of the flowering, you might want to use chemical or organics to flush your plants, if you use chemical you might need to flush the plants one and half or two weeks before harvest. If choose organics, one week is OK. Once you start to flush your plants, you should take more care on the bud rot. Bud rot happens when the humidity is high, looks like a black brownish sludge that can quickly take over your plant and ruin your harvest. The mold spores are air-borne.
Prevent and Control
Removing dead or dying leaves will help keeping the air flowing to decrease the humidity,
Decreasing the humidity can prevent bud rot, even though only decreased a little will have big difference. If the bud already rot, you can cut off the bad buds and apply any of the following: Neem oil, Neem2 which is a ready made solution!