Yeah, definitely some kind of mold that you DON'T want mixed in with your harvest... I'd snip out that leaf (looks like it's only on the leaf), examine the bud to make sure there's no more by trying to pull out other leaves around it (bud rot will go INTO the bud and if it's there, the leaves will pull out easily)... if you find more, you'll need to get rid of ALL of it. I'd then spray that area with a 1% hydrogen peroxide mix to kill off any remaining spores... the hydrogen peroxide will evaporate and not affect your harvest. If it's REALLY bad, you may just want to cut off that entire bud, spray and harvest as soon as you think she's ready.
Good luck!