If you are using a profile, you have to change the channel outputs in the profile.
In vixen:
Profile -> manage -> profile name -> Done
Your profile should be open now.
On the left hand side of the ouput names will be 3 boxes.
The top box (green and red) will let you change the channel output.
Put them in order, the first one will be the first channel of the first controller.
Changing the channel order (box) on the right side of the channel names will not change the way that they output.
Note: I have never used DMX, not sure if the same rules apply.