that appears to be Botrytis fungus, leaves mysteriously dry out on the buds. it attacks the inside the bud. flower bud will quickly turn into a slimy substance. you need to lower your humidity botrytis can destroy your hole crop in seven to ten day.
Control: Minimize Botrytis attack lower humidity to 50% or lower get good air circulation and vent room well. as soon as you noticed it Use alcohol sterilized pruners to remove the infected buds remove about one inch of the infected area,
some amputate 2 to 4 inches to ensure removal.
Do not let the bud or anything that touches it touch anything else it is spread very easy.
Spray plants with Gliocladium roseum and Trichoderma species.
Bordeaux mixture keeps early stages of Botrytis in check as long as it is present on the foliage, Preventive spraying is advised if in a high risk area,. but spraying it around your bud nearing harvest isn't advised You can also check with your local nursery for product recommendations.