Premiere Pro CC export produces dark, muddied video
In my experience Quicktime always produces incorrect shading and color with video- period. It shouldn't be used to assess what really "is there". 

First, go into Bridge. Under EDIT, make sure you've synchronized all your color settings for all Adobe Products, and that you're using WEB AMERICAN (Monitor Color for sRGB).  That would be the correct profile for web content like youtube. 

After that; try re-out putting. Also; you can check your NVIDIA settings; but you want to allow applications to control color; so it could be that your system is simply using a different color profile or an expanded color gamut for web vs what Adobe is using. 

But I'd shy away from using QT for viewing files (or anything MAC for that matter); having switched over to only using Windows based workstations so many problems like these have been solved for us. 

Hope this helps.