The bulbs in the display are probably burnt out. Need to pull display and replace the bulbs. The bulbs are usually dealer only so, you will probably have to get them there. If you have a matching bulb in another area of the display, You can swap them to make sure it is the bulb that has failed.
Did you check to see if the 'dimmer got turned down by accident? The dimmer (when headlights are on) should also control the backlights on your center console heater control backlights. IF they dim & brighten as designed , THEN I would agree that it's the bulbs in the cluster.