I grow outdoor and one PREVENTATIVE treatment I got recommended and use with success and you could too but ONLY IF YOU CAN TAKE YOU PLANTS OUT INTO THE SUN FOR A COUPLE OF HOURS, and this is for the future not now, the buds are too dense, it's too late for this plant... I use this ALL THE TIME in early autumn when grey mould conditions become perfect in my area, but you have to do it while buds are young and not dense...
Mix Milk with water. I use 1 milk / 10 water (can go up to 30% milk but 10% has worked for me) Spray on plant all over till dripping, you must do this in bright sunlight, allow it to fully dry in the sun. when dry you can take your plants back inside. The sunlight reacts with a protein in the milk that prevents spores from becoming active. I do it every 10 days before the buds get dense. I had grey mould all the time before this, now i don't