More likely your restart problem is caused by something else. You might want to monitor the actual glow plug voltage at the plugs during a cycle. There is a very slight chance you checked your old plugs with very low voltage.

Or there is for some reason not much voltage present in the glow circuit. If that was the case the new glow plugs are not functioning much better. If you do not own a cheap meter get one. I suspect you already do own one though. I also have no ideal what your regional temperature is there right now.

I would still tend to eliminate that glow plug circuit as a possibility first. Takes little time to do it. You should almost always return to the original fault area before moving on. I know I dislike going around in a circle on problems myself.

I hope and suspect not a cylinder wash down. I imagine a diesel could be slightly flooded by repeat attempts to start but should clear itself. It would take a lot of cranking to get much actual fuel in there and most would be blown out I suspect. The cylinder washdown angle is possible on a really marginal engine I imagine but do not really know enough about diesels to really comment. I also suspect your engine is not marginal.