Screen discoloration in top right corner of iPhone 6 Plus, please help

I replaced the front panel on an iPhone 6 Plus last night. I tested the LCD before installing all of the components (front camera, speakers, home button, etc.) into it, and it seemed to work fine. I even did one more test run before I closed the screen to make sure all of the cables were connected well, and it worked perfectly. When I closed the screen, however, a bright spot had appeared in the top right quarter of the phone. I have had two other 6 pluses with identically shaped and positioned bright spots, so something I am doing wrong must be causing this. Please help me with any information you know.