4K iMac Graphics Issue

I've recently been having a problem with my 21" 4K iMac. I believe it is only a driver issue but I want the issue to be solved. I purchased my Mac the day the 4K iMacs were in stores. Everything had been going fine till about 2 weeks ago when I was using photoshop and noticed my screen continued to flicker black when using the brush tool. Also when using safari if I have a Youtube video in fullscreen it bugs out the video and only shows half of it. Please help. Thank you.