Are all CCW props on the bottom, or all on top?
If yes that is not surprising because the bottom props are in the airflow of the upper props (downward + twisting airflow). Usually the bottom props need a larger pitch to compensate.
If this imbalance is an issue for you, for exemple if it takes too long for the yaw rate integrator to build up, let me know. It is possible to create a custom mixer that creates the imbalance from the start. A simpler fix is to alternate the CCW and CW props on top and bottom!