Hi,
Well it really would be very difficult to cater to light duration because the plants uptake nutrients all day, regardless of whether the light is on or not. A lot of things happen in the dark. The nutrient uptake is higher in the light, of course. In any case this avenue of thinking is not really the right path. The reason for limiting the light duration is that algae appreciate light much more than the higher plants do.
As a result, your observation of the diatom behavior, unfortunately, is in error. Too much light, in conjunction with the chemical instability of the tank triggers diatom blooms. Diatomic blooms can occur when the tank is first setup, but after a few weeks, if the light intensity is not over the top, the blooms subside and usually we don't see this type of algae again. Your Cuba was lost due to poor CO2, not due to poor light. Hobbyists often fall victim to observations of things in the tank that are circumstantial evidence. The fact that many people fall victim to this illusion and report their conclusions leads others down the same path, so the new victims increase their lighting and do not pay enough attention to CO2/flow/distribution implementation.
Do not overthink nutrition. The EI dosing scheme is made to simplify this aspect of plant husbandry. Margins of error are already built in, whether the intensity and/or duration are varied. There is a wide range of nutrient values that plants can use to be healthy.
Too many people look for a way out or extra methods of adjusting the dosing. I suspect that this is due to a subconscious fear of nutrients.
EI requires neither adjustments due to duration, nor testing of parameters. Simply dose the standard values and carry on.
CO2/flow/distribution as well as cleanliness are where the complexity and difficulty hide. Study and implement these other factors and I guarantee you will see improvements in your tanks.
Cheers,