Question League of Legends - low fps 9700k + rx6800

[MuHíí]

Hello guys,
I am having pretty bad time with League of legends right now.
I have 9700k oc to 4,9GHz with rx6800. 1080p 144hz monitor, but the fps in LoL are pretty bad. Game starts with 300+ fps which i would be happy but after like 2-3 mins, it drops to around 200 and in fights, it is around 120-150. Adrenaline from AMD is showing 129 average fps in LoL. I have 2x8 DDR4 3600 CL16, game is on SSD. Any other game works absolutly fine. Pushing 200+ fps in almost any game like nothing. With PC like that, i would think i can push 300+fps 24/7 on LoL but droping under 120 in game like that is pretty bad. Any solution or idea?

 

[Lutfij]

Welcome to the forums, newcomer!

When posting a thread of troubleshooting nature, it's customary to include your full system's specs. Please list them like so:
CPU:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
Monitor:

include the age of the PSU apart from it's make and model.

 

[MuHíí]

Here goes the specs:
CPU: i7 9700k oc 4,9ghz
Motherboard: msi z390 gaming plus
Ram: Crucial Ballistix red 2x8gb 3600 CL16
SSD/HDD: Samsung 850 + Kingston A400 + Barracuda 2TB
GPU: PowerColor RX 6800
PSU: Seasonic focus 550w Gold (2y old)
Chassis: Gamemax Aero
OS: Win 10 Pro
Monitor: AOC C24G2AE (1080p 144hz)