Hey Daniel.
Sounds like your sealed system may be working ok, as well as most other components. If the seals on the doors were bad, the system might be working fine, but the temperature in the frig and freezer would be elevated because the bad seal is allowing the cool air to escape. I say this primarily to show an example on this point.
Likewise, if the evaporator has an icy buildup it will create an insufficient cooling condition. This would result from something going wrong with the defrost cycle. Check the evaporator. If you find an icy buildup the problem could be with a thermistor, bi-metal thermostat, defrost heater, or the main control board.
If the evaporator looks fine, you may want someone qualified to check to see if the refrigerant charge in the sealed system is within spec.
Hope this helps. Good Luck.