Screen dimming and brightening at random intervals

[Nanoro]

While playing, my game keeps blipping between a few notes lighter or darker screen for no immediately apparent trigger. The interval can be ranging from under a minute to more than roughly 10-12, with little consistency.

 

Has anyone had this issue before? As a side note, while playing my other screen seems to experience a sort of lag, as well. I usually have YouTube on when playing and the video seems to sort of stutter as I'm tabbed into the game.