Attached is a primitive diagram.
All 3 rooms are on the same floor. Room B's vent is not blowing as much cool air as Room A's vent. Ive closed the vents in Room C and A. And still no luck. The force of the cold air being blown from the vent in Room B does not change. However, when i close B and A, one can notice the change in the pressure/amount of cold air coming from C's vent. Same thing is noticed for A's vent when C and B's vents are closed.
Any help is appreciated.