High memory consumption on SCOM DB server

Hi All,

I have 3 databases hosted on an instance (OperationsManager, ReportServer & OperationsManagerDW). Taking help of HelperSizing tool, SCOM DB server was designed with 16 GB RAM and as per Microsoft recommendations we have kept separate drives for system databases, user databases and log files. All fine until sometime, but the memory consumption on my SCOM DB server shoots-up day-by-day touching to it's MAX - 14 or 15 GB whereas the CPU utilization remains normal, need to restart the SQL services every 5th day to make it back to normal but problem still persists....

We are on SCOM 2012 R2, SCOM DB server: SQL 2012 with latest SP

No. of MS: 1, OS: Win 2008 R2

Monitored Applications: AD & Exchange 2010

No. of agents: 25

Nothing abnormal in the SCOM Db server OperationsManager log except below errors in the Application log & SQL server error log, which occurs every second. Any help or clue is highly appreciated....

Log Name:      Application
Source:        MSSQLSERVER
Date:          5/30/2014 4:08:06 AM
Event ID:      28005
Task Category: Server
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      SCOMDBserver.com
Description:
An exception occurred while enqueueing a message in the target queue. Error: 15404, State: 19. Could not obtain information about Windows NT group/user 'Domain\SCOM_SDK', error code 0x5.

Thanks