I agree with ChasBean1 that Air distribution within the space is of great importance.
Consider readjusting the direction of throw (perhaps away from occcupants) in order to improve the situation.
I am of the opinion that all pumps will be running at the same head since the run parallel against the same headers. Its just a matter of balancing to a new opearting point (common for all pumps). Increasing the speed of the variable speed pumps will raise the said balancing point.