blurry font in second chrome window
if I open a second Chrome window, all fonts and icons are blurry/jerky; this is also the case for the e-mail client Mailspring. what could be the case? here's a screenshot - the top window is the first Chrome window, the bottom one is the second one. If you view the screenshots fullscreen you can clearly see how the bottom window is unsharp...

PS in other programs and in the first opened Chrome window the fonts are normal and crisp; I'm running F27 and use 'Slight' hinting and subpixel Antialiasing in Gnome Tweak.
thanks
Fedora 27, proc: i7 2600K, mem: 16GB, card: Nvidia GTX970 4GB, ssd: 256GB Samsung EVO 850, audio: TASCAM US-100, keyb: Logitech K800, webcam: Logitech C910, graph.tablet: Wacom Intuos Pro small