iRule - Header Replace Blacklist

I think this would work, though for performance sake I would do it a little differently (and your strings are mixed case when you're trying to compare on lowecase)...

when HTTP_REQUEST {
    set host [string tolower [HTTP::uri]
}
when HTTP_RESPONSE {
    switch -glob $host {
        "*notthissubfolder11*" -
        "*notthissubfolder12*" -
        "*notthissubfolder13*" {
             Do nothing
        }
        default {
             Replace the header value
            HTTP::header replace X-Frame-Options "SAMEORIGIN"
        }
    }
}