Portals, Portals Everywhere!

I run a server and for the last 2 months portals have been spawning everywhere in my world.
If you jump in the portal that the dragon spawned after death, then you pop up in a randomly generated portal, or even if you make a portal to Nether it'll spawn random portals after you jump in.

How on EARTH do i disable portals or much less fix this problem? Its screwing up my spawn and other worlds!

Tried removing the portals manually, but they keep popping up randomly as people use them. D:

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

Plugins List?

 

I have the same problem with Nether. My plugins are:
·WorldBorder
·MultiWorld
·SimpleBackup
·St0rmIRC
·GroupManager
·HerobrineAI
·WorldEdit
·NoCheatPlus
·MotdManager
·SimpleAutoannouncer
·Vault
·CustomJoinMessage
·SimpleHelpTickets
·PlayerHeads
·LogBlock
·LWC
·WorldGuard
·SimpleWarnings
·Spectate
·Lottery
·PVPArena
·CapsLock
·AdminPrivateChat
·OpenInv
·ChestShop
·MobArena
·FoundDiamonds
·FreezeFrame
·Essentials
·CreeperHeal
·EssentialsSpawn
·EssentialsAntiBuild
·PayDay
·xAuth
·EssentialsChat

Hope you can help me. Thank you!

 

- xAuth?
Why do you have this?
Are these portals from making nether portals? or are these end portals?