Garry's Mod Server Help


I hope this is the correct area to ask for help with my current GMod Server.
I have had it running for just under 4 months, but recently it has had lag, not just the normal connection lag or prop lag, but FPS lag.
My current host said to remove all of the addons. I did so an there was an incredible reduction. I then started to add them slowly back over the course of a few hours and had bots join the server to test the FPS.
All was going well until the last addon. I installed it and there was no issue, but within 3 hours of the server running again the FPS lag was back. I have since then updated the server, updated the gamemode (DarkRP) and re-installed the addons again.
I then, last night decided to re-install the entire game server, just incase something had broken in the core files. It worked fine and ran sandbox with 115 FPS with 17 bots on the server.
I then installed DarkRP again and started adding the addons back. After I had installed 5 addons I then left it for a few hours and the FPS lag had returned. After that, i removed all of the addons from the server, including DarkRP modification
and after a couple hours the lag was back… Could someone please help as I have no-idea what to do. It isn’t the addons. If someone could help me to fix this I would be really grateful as I have a developing community with an average of 18 people on a day and they cannot play. Hell, you can hardly walk, let alone roleplay. Thank you.

Ok, ill move the post.