Known cause for server fps lag?

I currently host a TTT server and for some reason there would be huge amounts of fps lag for everyone when the server hits about 13+ players. The lag is clientside only and not server side, i have checked net graph and there wasnt any red at the very bottom. Just huge red at the middle of net graph. I am sure it isnt my graphics card because i run on a 560ti. Does anyone know the real cause to this fps lag? Could it be a specific playermodel or pointshop item such as trails or hats? Or is it addons coded badly? Does anyone have a clue?

If the lag is clientside why you put “server fps lag” in the title?

Anyway, the are too many causes for this to list them all:

Bad server coding
Bad server coding
Bad server coding
Missing materials?
Bad server coding
Big Hard Drive Disk usage
Bad server coding

Hmm although i am getting these red errors in console

Requesting texture value from var “$dummyvar” which is not a texture value (material: NULL material)

KeyValues Error: RecursiveLoadFromBuffer: got EOF instead of keyname in file materials/models/zombie_classic/zombie_players_sheet.vmt
VertexLitGeneric, (proxies), (Clamp),

Verify integrity of game cache

Is it just yourself getting the lag or is everybody getting it?

The largest killer to servers is ragdolls and player models

Everybody is having this problem. A guy with a 670 was also lagging badly at certain times.

[editline]17th June 2014[/editline]

Is there a way to reduce this amount of lag? Like maybe a code to remove the ragdoll after being identified

What map does this happen on? Every map?
How many addons do you have?

You really need to give some more information about things, not just what happens.

This lag happens on mostly all of the maps, but is more intense on maps other than cs:s default maps. And i have about 19 addons, advance ttt, csgo hud, csOS, damagelog, map vote, hitmark, modernmotd, pointshop, psdrop, chatbox, ulx, hit points, cl_leg, ttt role counter, utime, ttt stats, and ttt endround music. I have checked the clientside error text file and console text file and i didnt seem to find any error spam. I dont know if knowing the tick would help, but my server is 66 tick.