A grey background on your prints is usually caused by a few comon things. One of the most common issues is a dirty or worn-out drum or fuser, which can cause toner to spread unevenly. It could also be that the toner cartridge is running low, defective, or if you’re using an aftermarket cartridge, it might not be working properly. Sometimes the problem can come down to printer settings, double-check to make sure you’re not using something like "Toner Save Mode" or similar settings that might affect the print quality. Paper can also play a role, if it’s too thin or textured, the toner might not adhere properly, which can lead to shading. I’d start by cleaning the printer (if possible) or trying a new toner cartridge to see if that solves the issue.