Can I verify that VIP is doing the right job ?

Hi, it's strange that you have same pool on both VIPs, but different monitor. I think that pool name is different, then you can configure same pool members, but different monitors. If pool member is red, then LB is not sending any traffic to it. Why they are saying that traffic is from VIP B? LB is not sending VIP IP to the server, if you are not putting it to http header by iRule for example. I think it's rather traffic from VIP A and you can confirm it by tmsh command: show sys connection