I had an HDMI cable plugged in for a while that connected to a TV with no power. The retina display randomly flashed blue after a while and then changed to a different resolution (possibly 1080p). I unplugged the HDMI cable and nothing happened. So I restarted the computer to no avail. I was still having issues. So I fiddle with some settings after plugging in the HDMI cable again. Now, the retina display appears fine when no HDMI cable is plugged in, but when there is one plugged in, the resolution changes.
I have mirroring turned off (which is what I want). The resolution of the retina display when an HDMI cable is plugged in is 3,360px x 2,100px (according to the size of a screenshot) and the external display is 1,600px is 900px. How can I fix the retina display to show with the correct resolution.