Possible memory leak?

Hello everybody! As the title suggests, I might be dealing with a memory leak? When I boot up the game I have ~240fps in my hideout. The more I play the game, it gets worse and worse. After 2 hours of gameplay the same hideout goes to 108 fps MAX. I was checking my gpu/cpu usage/temps and i must admit my gpu was surprisingly low ( 25-50% at max during heavy juiced maps ).

CPU : I9 12900K
GPU : RTX 4080 SUPER
RAM : CORSAIR VENGEANCE DDR 5 5200 MHZ


INGAME:
Build: Ice Nova of Frostbolts with cosmic MTX.
Power charges speheres mtx
New league weapon enchant (the blue one, can't remember the name)

I was thinking maybe there's an issue with the MTX i have? I was wondering if anybody else has these issues. I'm pretty sure my pc should be able to handle the game at ~160-190 fps while mapping. Also need to mention I'm running 240hz 1080p monitor. Also, everything under settings is set to LOW.

Hope anyone can help out as this drives me crazy! Thank you very much people!