How can I switch control between the four decks while using the Numark Mixdeck Quad? It seems to only control decks one and two.

When i use all four decks in Djay Pro on my iPad Pro and controlling with the Numark Mixdeck Quad, It seems that i can only control the two middle decks. The two outer decks i can only manipulate by touching the ipad screen. I’m sure there has to be a way to switch control between the decks with the Mixdeck Quad. Can this be done? And how?