Different connection status between 2 servers

Hello All,

Actually, We have a problem in our server (RHEL 7.1), 1st server is used for payment apps like switch card payment (passthru only), and 2nd server is used for Database transaction.
When high transaction there is different connection between Apps Server and DB server, Apps Server sends connection to DB Server, but sometimes that's connection not ESTABLISHED like low traffic (I checked thru netstat in 2 servers). I have changed value Local_port range, and fin_timeout but it wasn't solve this problem, and I think my current kernel needs to update kernel to latest or stable version to solve this.
current kernel : 3.10.0-229.e17.x86_64

Please give me suggest about our this connection problem.

Thank you
Regards