Bud rot?

Yes, it is. Cut it off now and pray, It might already been on other breanches.. if you have lots of plants, throw this one off a distance!

This is a fungus infection or powder mildew infection, progressing to bud rot. You can also spray the infected areas down with diluted isopropyl alcohol, it will get rid of the fungus spores. This is only safe for edible consumption though. As smoking it would be very toxic. The Isopropyl alcohol is safe because it is used in R.S.O.

I cut the plant down to avoid cross contaminating the other plants. Most of the plant looks good, but I found a lot of aphids hiding away in there. Is there an issue smoking the bud if it doesn't have any damage to it?

Either heat damage or botrytis. I wouldn't take the chance. Sorry mate.

@ChitownCannaChica I looked closely, but I can't see any of the mold. Can it be from heat? It's dry and hot here in SoCal, so I am wondering if it's not something else? What can be done if it is mold? Are other plants safe? Thanks for your reply.

Yes, sorry my friend! It’s bud rot. Botrytis