Original post by: Reece ,
Could be liquid damage (can cause a light patch where the liquid leaks onto the LCD) or the white mark could be caused by impact damage to the LCD, difficult to tell without seeing it. Are you able to add a picture? In terms of the touch issue, has the iPad glass screen been replaced before? May not have been insulated properly by the company who did the repair. If not, it is again likely caused by liquid damage.