Lag issues

Hello, So recently I've had extremely bad lag issues in league, and only league. Firstly, when i play in normal's or competitive, about halfway through the game(30-40mins) my game will just go, NOPE. And then preceding to not follow any commands or show what is happening in the game. However while that is happening, all my movements and spells casted, are shown like normal to other players. Then finally, when i try to have two of my computers playing league at the same time, my alienware will work perfectly fine, and have 20ms, but then, myself having a same problem as my first. Anyways, thank you for viewing and any help is welcomed!