Originally Posted by Drip

Skill Blooms are a random drop from the boss of ?-4.
Dress Blooms are a random drop from the boss of ?-8 (At least, if they fixed ?-8, but we shouldn't see that map with that mechanic ever again)
Drop rates were supposedly 50%, and Blooms might drop from their respective lower maps as well, but at much lower rates.

You could get them from ?-3 as well but at a much lower droprate if memory serves me well. Either way this sucks for us who already did this event.