Cannot Adjust Headphone Mix + Volume In Software

I use a Native Instruments Komplete Audio 6 as my desktop PC's audio device.  A brand new DDJ-RX is connected to my PC via USB.  My speakers and headphones are always connected to the Komplete Audio 6.

Once the controller is powered on, the Headphone Mix + Volume knobs in rekordbox gray out and cannot be adjusted.  As you already know, the knobs on the front of the DDJ-RX controller are hardware only and do not control the software's headphone settings.  By default, the headphone volume coming from rekordbox is lower than the master output and the headphone mix is set to 100% cue, with no option of turning a knob to bring some of the master into the headphones while cueing.  These two knobs can be adjusted before powering on the controller, but once rekordbox detects the controller, it resets the two knobs to their default settings.

Why is this?  If the two headphone control knobs in rekordbox would be activated instead of gray, this could be adjusted as needed.  Disconnecting my speakers and headphones from my audio device and hooking directly to the DDJ-RX every time I want to use it is inconvenient and unnecessary.

Thanks very much.  :)