I then shut everything down, removed the boards from the miniplane, plugged them into 4-pin molex connectors, and powered everything on. The two LED-less boards remained green ghosts. I then returned everything to the miniplane, powered it on, and have been consistently and stably hashing on the two responsive boards (at ~19gh/s per board with default settings) for the past 16 or so hours.
I'd rather have a green ghost than a no green dead board. At least then you have some power to flash if its a firmware issue. Maybe at least in that state barntech can send you the current firmware or a better firmware they're trying and try to push it on to it.