As you can see the below images posted by different users facing this issue in their yu yuphoria.
#How to fix white lines in yuphoria display
So how can you fix it or prevent coming white spots on yuphoria screen?
If you are using any type of screen guard or tempered glass then just remove it as it can be the major reason for this problem.This problem can also be due to leakage of display or pressure due to extreme heat so if your device is less than 2 months old or more then you can ask for the replacement unit from Amazone.
They will surely replace your device within a week and you will get a new yu Yuphoria after 1 week or more according to your location.