I apologize for the inconvenience caused. To assist you better, please post a snapshot of the smudges that you see on the monitor.
Meanwhile, do you observe green or pink tint on the monitor? Also, ensure that there are no electromagnetics devices like microwave nearby.
Also, you can try resetting the monitor settings to original configuration. Please follow the steps below:
1.Select the Menu button.
3.Select Other Settings, and then Factory Reset.
4.The screen will display the words Auto Adjustment in Progress.
5.Once done turn On and Off the monitor and check.
Thanks and Regards