I have no ground either, just a common zero volts line from the drivers to the LEDs. The ammeters were in the positive voltage line to the LEDs.
Another possible problem: I have two different kinds of optics. One is for the XM-L and one for the XP-E (Not XR-E, as I thought) Which is for which LEDs??
Both can fit either LED, but the tiny one "snaps" onto the XM-L LEDs, and the other one has to be attached with adhesive to either LED