New Refrigerator Past Warantee Not staying cold. I have a two year old Kenmore R134A refrigerator

Question

I have a two year old Kenmore R134A refrigerator with top freezer that just started not staying cold. The freezer is OK but also seems not as cold. Bought it brand new - past warantee though and not sure what to look for.This is a 6 1/2yo unit (I think this is the product number) and first was not getting cold on freezer side so emptied it looked for frost etc and brushed/vacuumed/cleaned accumulated dust from condenser coils and have an intermittent problem with loss of cooling--compressor runs smooth and quiet..at time may not be cold (ie 50F) and then that PM 28F in freezer..naturally with single compressor the refriderator side seems effected too although initially it did not seem to be effected ( it too is sporadic as cool right now)