sounds like something wants to eat your buds, ive seen slugs fall from trees into the roof of my green house, and screw up some plants. Basically they would drop in from the roof land on a bud, leave a weird residue.
Then the sun comes up and heats it up, sort of scorches that area they were on. I caught 2 of em in the act one morning at 4am.

birds?
fungus?
cold/frost?