After considering your problem further, I wouldn't worry about the fuel racks. I think that, since both engines won't start, that you definitely have a fuel quality issue.
You may have water...a lot of water...or...algae....or both... in your tanks.
Water is heavier than diesel fuel. Therefore, diesel will "float" on water. Your pumps pick up tube sucks fuel from the BOTTOM of the tanks. If there is water there, then water will be drawn into the fuel system first. Lots of water...no burn.
If you have drains on your tanks, try to get a gallon or more as a sample and see how much is water and how much is fuel. Do this when the water is calm so that there is no "mixing" and you can accurately determine how bad a problem you may have.
All diesel fuel will contain SOME water. And that is why, in warm climates, algae will grow in your tanks. I've seen it over as 1/4" thick slime on the walls of small sailboat tanks. It will slough off of the wall of the tank and get in the fuel lines and filters and really gum up the works.
If you have algae... or water... or both... in your tanks, you will need to clean them and the lines before starting the engines. If you try to run the engines with water in the fuel lines, you will ruin EVERY ONE of your injectors.
You CANNOT solve the problem by just adding more fuel.
I would say that you may need to ask around the docks to find experienced captains or boat engineers to get some advice about what to do for checking and, if need be, disposing of your old fuel.
Good luck.