It could be balance point... or it could have just been one of those days.
A lot of times, when the arm drags behind, it has more to do with the timing (and location) of the hand separation rather than the balance point. The next time you throw a bullpen, work on speeding up your hand separation (as soon as the balance leg starts downward). It'll allow you to get into the high-cock throwing position quicker. And it'll allow you to keep your fingers on top of -- and behind -- the baseball.
Let us know how it goes.