Hi Vijay,
did you activate the Oneconnect feature in your VS?
For info:
When a OneConnect profile is enabled for an HTTP virtual server, and an HTTP client sends multiple requests within a single connection, the BIG-IP system is able to process each HTTP request individually. The BIG-IP system sends the HTTP requests to different destination servers as determined by the load balancing method. Without a OneConnect profile enabled for the virtual server, the BIG-IP system performs load-balancing only once for each TCP connection.
https://support.f5.com/csp/article/K7208
Regards,