I have just gotten a MacBook Pro retina Early 2015, which I want to connect with non-retina external display. I'm using a VGA to display port adapter to connect it and it does work. However the resolution is not correct. It's all blurry. I have tried to option click the scale button in display settings and tried them all. Non of them seem to fit the screen. When using HDMI instead it works like a charm. Am I doing anything wrong?