Whirlpool Gold Refrigerator not cold, Freeze is fine

Have a Whirlpool Gold 4 years old.

refrigerator is not cold, but the freezer seems fine.

there is frost build up on the back of the freeze section.

When I check for air coming out in the top back of the refrigerator,
There is no air when the freezer is closed. When I open the freezer door there is cool air coming from the vent in the back / top of refrig.


Will Defrost work or should I move on to the next step.

thanks for any help. figured I'd try to fix before calling someone.