AC mostly only cooling on drivers side

As the heat increases I noticed the passenger side does not get as cool as the drivers side. I am thinking since the passenger side is cool(not cold) the 8yo system needs a boost of refrigerant. Thought please

 

You are low on refrigerant. Many cars favor the driver for AC when the system is low on charge. Go get the system charged and you should be back to normal.

 

Low refrigerant can cause one side to be colder than the other but if it's a dual zone it can also be an actuator/blend door issue.
A quick check to see if it's a refrigeration issue or not is to check the suction (larger) line where it exits the firewall in the engine bay.
Engine running & A/C on high the line should be cold, if it's barely cool or not cool at all you have a refrigeration issue. If it's ice cold then you likely have a blend door/actuator issue.