Refrigerator/freezer not cooling

My 6-year old refrigerator required highest setting and was still just barely cool enough all summer. Then about two weeks ago it started working fine with freezer reaching 0 degrees. Today temps in both freezer and frig are at 50 degrees. The condenser and freezer fans are running. The compressor is warm (not hot) but discharge line not cool. I have started /stopped defrost cycle (can’t tell which is which) a few times with light switch but it makes no difference. Can anyone help me?