Low FPS?

I've got a Dell 15 Gaming 7000 series laptop, and lately I've been getting a lot of FPS drops in some games. Most notably League of Legends and Injustice 2. Previously, I had no issues with League whatsoever, and no issues with Injustice 2 during the beta (just bought the full version).

I did recently buy a new Targus universal charger because my old charger that originally came with the computer broke. Could that possibly be the cause?