Plugin Help Can't use Potions

I run a kitpvp based server with soups and potions, recently some of my member couldn't use potions, but my moderators could.. Here is my list of plugins:

King_of_the_hill [Koth]
WorldEdit
Buycraft
PVPDrops
PlayerParticles
FullHunger
Vault
Multiverse-Core
PermissionsEX
PlayerHeads
WorldGuard
Reporter
ClearChat
AutoBroadcaster
ChestCommands
Simple1v1
ClearLag
NameTagEdit
Essentials
BattleKits
EssentialsProtect
EssentialsSpawn
EssentialsAntiBuild
EssentialsBuild

Yes I do understand this is alot of plugins, we are in the phase of deleting BattleKits to our own plugin which has the same things but has a better GUI and Command features.
If you could help it would be great! Thanks!
-Willow