RX 460 4GB OC- Low Perfomance

hi everyone

since the last patch (17.8.2) i have been having some low perfomance with my video card while playing League of Legends; the game used to run with all graphics settings at max at 60 fps and it never changed....until i upgraded the driver, and now sometimes it goes down to a minimum of 20 FPS in non-repetitive situations(example: it NEVER has a low perfomance during TEAMFIGHTS during the game but it can happen when just pushing a lane or destroying the nexus...of viceverse) and it happens during 10-20 seconds

hope you guys can help me please, because it is kind of anoying, i brought this video card 2 months ago,it used to work perfectly, so there is no way the issue can be provoked by ``the age``