If it were just one engine doing it, I might be inclined to think that the "white smoke" could be steam. But, since it is happening with both engines, it is more than likely raw, unburned, atomized fuel. This will occur on high hour units that have worn cylinder kits or, as Marv suggests, sticking compression rings. Again, since it is happening to both units, it is more likely that they are just equally worn.
You can usually determine that it is fuel just by smelling the smoke. If it is, then you pretty much know that you are not losing prime. Personally, I would not be too concerned about a 5 to 10 second crank up after a long cold soak. I've seen these engines take much longer than that to crank and build heat because of normal wear and still provide good service..
Not sure what is in that turbo inlet housing in the picture. If it utilizes an air filter cartridge then you can"t do what I'm about to suggest without opening it up. But, if it is just a resonator with screen baffles, you can spray a burst of WD-40 into the intake prior to start up to see if that helps the condition.
DO NOT...REPEAT... DO NOT USE ETHER as a starting aid! WD-40 will not damage the engine and ether will...even when used correctly. As a matter of fact, imprudent use of ether will result in the damage that causes long crank times and white smoke. In the business, we call these engines "ether babies" as, ultimately, that is the only way that you can get them to start.