Server LAG

Hello this is the 3rd day that i have my server and my players lag not when they break a block but when they chat or type a command.

my plugins:
DigitalClock
groupmanager
WorldEdit
NoCheatPlus
VoxelSniper
PlayerMarkers
RamCheck
SecretPassage
Vault
Multiverse-core
SignColors
WorldGuard
Iconomy
PVPTag
RateOfXray
Lockette
SavingPlus
QuickSignReloaded
Essentials
EssentialsProtect
EssentialsSpawn
EssentialsAntiBuild
AuthMe
EssentialsChat
Factions
SafeCreeper

i think that the problem is the ram now my server runs with 249 MB of ram so can you please add me some ram? if you can can you make my server start with 2 or 4 GB of ram if you can then this will be great!!

my sever number is