Server Based Networking Reduce Lag

I have a completed networking game however, there seems to be a bit of lag when playing with multiple people. Basically, I have everything created on the server and when a player joins and leaves are the only times that the clients are sending messages to the server. The server holds up to six players and 6 balls, there is an rpc call when someone scores and there are up to 9 other items that are just instantiated and destroyed across the network. I am basically wondering if there is an optimal amount of network objects please let me know.