Activated Niagara plugins in UE4.25 and and older game in UDK runs really sluggish

Curious. I just activated the plugins of Niagara in 4.25 and suddenly an older game of mine I play with friends that was built in UDK runs really sluggish. Even worse with OBS recorder. My other games and Unreal 4.25 project runs fine. Does anyone know if Niagara plugins in 4.25 somehow messes with UDK (Unreal 3) runtimes?
Very strange -_-

Steam and OBS and Nvidia drivers are up to date.