Hi there! I have just received my new Retina 5K iMac (i7,16GB RAM M295X, 512GB SSD)- its great!! However i am experiencing lag with my Logitech MX Perfomance Mouse. I have two external 1080P monitors connected via mini display - HDMI adaptors, and the mouse cursor seems to lag. It seems to just be the mouse as the Magic Trackpad does not do this at all. I believe it is something to do with the two external monitors as it was fine without them connected, i also experienced this when i connected my RMBP to an external monitor. If anybody could help or has any advice then that would be great - Thanks!!