How did LoL get stuttery with my below average specs?

I am playing on a HP MiniPC 705 G5.
3400G
16GB ram 2933mhz
RX560X 4GB

Updates happened and now the game is often below 60FPS.
I do not ask much of it, but it gets me even worst.

I tried some online guide, something a little fixed it but really I could play it on lower specs.
I tried on my GF's PC and with the 5700G integrated graphics this did not happen.

What shall I do you wise men?