Hey Evelyn.
So, it sounds like the original VIP is inserting an x-forwarded-for address (client ip) then passes the connection back to the Apache server. Doe the Apache server call into a VIP for the App Server? is that VIP set up to also insert an x-forwarded-for? If the App Server VIP is only going to be used for web service type calls, just pull that part of it out and as long as the Apache server is set to send along the original x-forwarded-for information, it should arrive at the app server.
Or course, if it's a direct call from the Apache server to the App Server, the F5 won't be able to do anything.
HTH
Cameron