Dude, I feel for ya. Bud rot is an nasty thing and tends to go much deeper than you can physically see on the surface. It's a hard lesson to learn but very valuable aswell. The humidity of your grow room whilst flowering was probly the cause.

Make sure to trim past the rot... at least an inch imo and get it gone. Dont handle any un-infected parts after you've touched any of the rot or u will unwittingly transfer the mold spores. Id also dry it as quick as you can.

I'd throw any mouldy weed away. I had some mouldy weed and I thought what harm can it do. I smoked it and half way down the joint I felt my lungs going really tight. I could only take very shallow breaths and if I tried to breathe deeper I would cough, which made me breath deeper, which made me keep coughing in a viscious circle. It was quite a scary experience and Id never smoke mouldy weed again.