Seeing as how it is a symptom that arises from an increased resolution, I'd say it is definitely an issue with the gpu and isn't likely to have anything to do with the cpu. If you have not already done so, I would suggest using driver sweeper to uninstall your current graphic drivers and install the most recent version. Make sure to use driver sweeper before updating.
After doing that, test the games again and see if the issue persists. If it does, then make sure monitor the gpu stats in game (temp, vram usage, power usage, etc.) If nothing looks out of the ordinary, then it could very well be a defective power supply.