Help with Reverse Proxy iRule

I would start by looking and the HTML source to see the path of those CSS/images and make sure your rules would target those paths. Also, a switch statement would be a lot easier to read and maintain IMNSHO (and it's faster).

switch -glob [HTTP::uri] {
    "/app1*"  {
            stuff...
     }
     "/app2*" {
            other stuff..
     }
     default {
            some default behavior to catch non-matches
     }
}