Hello, If you notice frost accumulating inside the freezer back wall, it would of course affect the coldness of the fridge since the fridge is only drawing its coldness from the freezer. So if there is frost accumulation, it might mean that you could have a defrost issue. Here is an article on how defrost works. Please click the blue word. It would help you better understand how your defrost system should work.
But then again, it could also be just an issue of a door left ajar.
So to be sure, we normally suggest customers to do a complete defrost of the unit first before replacing parts one by one. You can unplug the unit for 24 hours with both doors open and then if you notice that there are no more water dripping on the back drain pan, then you can plug it back and observe if the frost would come back accumulating inside the freezer back wall.
If it does, then we would check the defrost heater, defrost terminating thermostat, as well as the timer, either electronic or mechanical one.