There exists several fixes that must be used in unison to achieve a proper air balanced home. Things like;
1. Address the insulation package for each room that is out of balance and adjust accordingly. You may have to add quite a bit of insulation in those rooms with the many exterior walls and floors, so they can reach that ideal Air Balance.
2. Look at the windows in the unbalanced rooms. You may need to upgrade those windows in the rooms that are most affected by Air Balance issues. The insulating quality of your windows should be addressed by the homes original builder and where those better windows were needed should have already been installed to satisfy the rooms CFM requirements.
3.Properly sized ducts. Instead of just adding vents to increase air flow to a room, check into the duct size as well as the relationship of the location of this room in reference to the HVAC unit. Sometimes all a duct needs is to be reduced to increase the air flow to the affected room.