Lighting complexity view is black and textures blurred?

Hello, I have been working on a level and everything was fine for a while.
But since recently, my textures have started appearing blurred in the lit viewmode and the lighting complexity view is completely pitch black. Where did I go wrong?

Note: The textures become crisp and clear again when i open the texture file in the texture viewer/setting. But it blurs out again after a while while I am moving around in the content browser.