Spotlight licensing with federation

I currently have one diagnostic server monitoring one server room and 2 seat-based licenses for myself plus one other to use the client console.
I'm investigating what would be required to expand this to cover multiple computer rooms and am looking at putting a diagnostic server in each room and federating them all together and then accessing the federated view from the client.
My question is, Do I need more licensing to cover doing this?
When we originally purchased the product we were offered a site-license, but as it was only me that was going to be using the solution, this was too expensive and we instead bought a seat licence for myself. We then later bought a second seat license when I got an assistant.
Hope this all makes sense!