It sure sounds like the glow plugs to me. I spend a few months trying to track down my gp problem. First I bypassed the connecter that carries the heavy current to the contactor. Then I replaced the controller. Then I replaced all the gp's even though they all tested good. Then I put in a new harness. I finally found the ring terminal on the 2 heavy wires carrying current in to the contactor (controller) was bad. It showed hot most all the time, but wouldn't supply the necessary power. I stripped the wires, put on a new terminal and it has been great.
Start by testing all of your glow plugs. How long does your WTS light stay on?
EDIT: I just saw all your gp's are new as are most components of the system. I would run BRAND NEW wires from the fender mounted solenoid to the constant hot terminal on the contactor (relay looking thing on top of the controller). The new wires would replace the (2) heavy power wires that supply power to the entire gp system. These wires carry so much power, they were undersized from the factory and are a known problem area, specifically the first plastic connector mounted on the passenger wheel well if you traced the wires back from the contactor.