Can't P Rank 1-3!

Hey, as the title says I've had run after run after run and I cannot for the life of me P rank 1-3. time and style aren't the problem, it's the kills. I finish off all of the enemies in the red skull rooms and the blue skull rooms, and even the secret swordmachines. every time it's an A for kills. my only guess is that some enemies must be falling to their deaths in one of the rooms, which doesn't count as a kill?