If the windows are dragging the motor will request more power from the alt/batt.

Now, you need to find the reason why they are slow, Glass dragging or motor needing service ? armature tracks and brushes into the motors could be needing a service.

ANYWAY, do it a favor yourself, get an alt able to source 45-55 amps minimun at iddle... the more, the better, but at least that. TRUST ME. The charging system ( including ammeter ) will be more relaxed