Garrys Mod server fps drop

Hi,

I just started up a server and I seem to be getting FPS drop and I don’t know why. Ive tried it on my personal machine and my Dedicated server and still lag. both machines are capable of handling a server as I’ve had a server with no lag problems happening before.
So when I start I get about 100fps then over the time of about 2 minutes it drops to about 18 - 20 and I have no idea on how to fix it.
My server currently is running the deathrun gamemode on a map both ive had no problem before untill now

if anyone has had a similar issue then have you found a way to fix it could you please share or if anyone knows whats going on.

Thanks

Alex

Are there any console errors or any errors for that matter happening?