I can only guess but i belive you have used the Leap SDK to implement Leap Motion.
There is a new Version of the Leap SDK which allows the usage of multiply Leap Motion Controllers, it would be pretty nice if you could update to that Version.
Described here > http://blog.leapmotion.com/multiple-devices/
Download here > https://github.com/leapmotion/UnityModules/raw/feat-multi-device/Multidevice%20Service/LeapDeveloperKit_4.0.0%2B52238_win.zip