Easy to check your actuators for both sides.....
Either go to ECON mode, or disable the compressor......
Disable dual mode......with thermometers in the outside vents, slowly go from full cold to full hot(car at normal operating temp).......do you get the same readings from both sides?
Now set temp at the midpoint......go into dual mode......raise the temp on the passenger dial.......is the output higher than driver's? Now lower the passenger dial......is the output lower than the Driver's side?
If yes to all, then most likely you are low on R134a....