2 phones of mines have these white lines on it and i don't know how it happened. Anyone know what happened. I shared a picture of it?

It happened to an lg g5 and an iphone 6 i believe. The picture is of the iphone. I have no idea how this happened at all. The LG g5 wasn't in great condition but the iphone was perfectly fine with no problems. 2 phones of mines have these white lines on it and i don t know how it happened. Anyone know what happened. I shared a picture of it

This could be water damage, sweaty pocket, steamy shower, dunked in water.

This could be drop damage, dropped and knocked a ribbon cable loose, cracked a solder point on motherboard near ribbon connector for screen.

This could be heat damage, from leaving the phone in the sun, in a hot car, under a heated blanket, etc.