Problem is this isn't a "struggling to ignite the fuel" problem... this is a "not getting any fuel" problem.

Its literally acting like its not getting any fuel at all when warm. No haze or smoke... no spitting and sputtering.. no smell out of the exhaust of unburnt fuel... nothing at all when cranking once warm.

In other diesels I own, this is an indicator of an overly worn injection pump not being able to build pop pressure at cranking speed once the pump and fuel in the pump are warm.