Abillities,summoners and mouse cursor delays

Hi fellas! I have a problem with in-game gameplay At some point in the match like around 6-8 mins,i have delays with casting abillities,using summoners and some weird mouse cursor delays. It feels like a lag but my connection is fine,its not even with the frames Example,i usually play on mid,when the game starts its fine.When it comes around 6-8 minutes the delay starts happening His Q Sear His W Pillar of flame His E Conflagration Even and his R Pyrocalsm,has a delay on casting The whole thing lasts for like more than 3 minutes,every single game. Same thing happens even on other games like CSGO,CSS etc. but its not happening so often like it does in LOL.. My question is How can i fix this problem,are the games the real problem or my computer? Thanks![sg-soraka]