DJM 750 Up Fader

Hi,

I have connected my DJM 750 to Rekordbox 6 using performance mode, I am using CDJ 2000 and I have set up an aggregater on a mac selected that in Rekordbox and also external controller.

Everything works fine but when I move the channel 2 / 3 up faders up and down the sound reduces BUT the LED remain the same?

Any ideas

Nick