Is it just plain 80g/m laserjet media being used ? could need fuser settings changed to heavier stock.. Ghosting is normally the result of fuser unit/fixing unit or Toner cartirdge or media settings not set correct and not fusing the toner correctly
You could also try cleaning the paper path or sending a few cleaning pages through the printer using the Calibrate/Cleaning menu
At the product control panel, press the Home button, select the Device
Maintenance
menu, and then select the Calibrate/Cleaning menu.
Print Cleaning Page