Server Issues

Hello,

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.

[editline]7th April 2015[/editline]

Ok, seeing as I have also asked the DarkRP forums for some help, ill copy across the messages.
Someone asked for the addon list. Here are the addons I currently run on my server.

3D2D Textscreens
3D Car Dealer 2
Advanced Duplicator 2
Admin Bubble
AWarn
CAC (Anticheat)
Handcuffs
Custom Commands
CustomHQ Weapon Checker
CustomHQ Rad-15
Customiablemoneyprinters
Daily Login Bonus
DarkRP Weed
DarkRP Modification
Elegant Crash
Enhanced Sawmill
Escape Menu
EZInventory
GCAP
GModCentral
HHH_0.9B
Highscore
Itemstore
Keycard
Mining System
NPC Tomascustoms
P_NLR_Zone
Pointshop
PropCommands_Z4
Purge
SpawnProtection
RDM Manager
SChat
SScoreboard
SteamGroup Rewards
Stungun
Teletaxi
ULIB
ULX
VCMOD
VCMOD ELS
WireMod

If you would like the links to the page for any of them, dont hesitate to ask and ill provide the ScriptFodder link.