Help with random drop in FPS for no reason (only league)

Hello, i would like any advice with my problem. For some reason my game has had a significant drop in FPS for no reason, I used to get around 120 FPS on high settings and then out of nowhere with nothing happening to my comp I am now getting around 30. The crazy thing is is that only league has had this FPS drop and my other games are fine still on high settings. Another thing is that when i put my graphics on low my frames dont even go up at all its still around 30 fps. Ive tried doing a reinstall and that didnt fix it ( the one through client i havent tried deleting it completely yet) and i even set league to operate on my Nvidia 960m GPU and still no budge. this has been a problem for a while ( i think it first appeared during season 8 MSI and i thought the drop was just the extra map effects maybe) however i never really had the time to look into it until now and i cant quite seem to figure it out. If anyone has encountered this issue or might be able to shed some light i would very much appreciate it. Thank you for your time and cooperation in advance.