Game suddenly become so lag(game laging not internet)

Today's first game i had a teemo in my team. After 10mins he said hes so lag and start to afk. I did not believe him and obviously gived him a report.(all my team gived him one). On my third game, it happened. Game become so lag as my PC CPU/Physical memory both free. My ping as 70. I thinki its something by the new update. This is terrible. I also feel sorry for my report and im going to gt reported as well. It cost me 2 games already. Plz fix it