My refrigerator had started getting warm and the

Check the following:
1) Door seal gaskets for any wear and leaking - You can use the dollar bill trick between the base and the seal, close on it and try pulling out the bill, you want a little resistence - if the bill comes out easily your gaskets are not tight. (although this sounds like unlikely in your case)

2) Condensers at the back of your unit or at the bottom - using a condenser brush and vacuum cleaner, get rid of any excess dust - if your condensers are covered with excess dust your unit will not get rid of the heat efficiently and cause excess runtime on your compressor and it will take much longer to cool.

3) shut off your unit and remove the back panel of your freezer, look for excess frosting on the evaporator coils - using a blow dryer, manually defrost the evaporator and surrounding areas until everything is clean. Put the panel back and turn the unit on for a couple of hours, then check the cooling - if it returns to normal then you have a defrost problem and will need to have your control board serviced and check for the defrost timer components. Also make sure the evap fan is working and spinning normally. You also want to check your condenser fan at the bottom of your unit (if applicable, if you have condensers at the bottom).

If all else fails you will need to have service check your charge levels on your compressor and locate leaks if applicable - but the most common causes are defrost problems so check this one first.