Some plant strains need more nitrogen and calcium during budding than is usually available in composite nutrient mixes. You have to find the mix that works for your strain and dial it in. Blueberry for example asks for a bit more N than is usually available in nutrient mixes around week 3 of 8 weeks of budding, but strawberry cough is the opposite and can easily be over (N)'d using say Canna Tera Flores NPK of 10-9-19.
I would agree with Willmunny on this one because I think you are too far along in budding to be trying to up your nitrogen by any serious amount just to save the shade leaves. But you never know, and I suppose its something you need to try once, and if it screws the budding cycle then add that to the list of things never to do again.
The reality is that the nutrient companies are not really killing our leaves with low N bloom nutrients, most mixes provide lots of nitrogen in their budding formulas.
Each grower has to dial their crop in as each strain has different demands. The biggest killer of plant leaves are growers. There are growers who continue to shock their plants during budding by continually plucking off leaves that dont look sexy, changing light cycles, light shocks from entering grow rooms with lights out, light shocks from grow rooms not properly light tight, and lots of other environmental shocks caused by growers - like pests entering the grow room because of bad design or coming in on the grower themselves, to name a few.
Another big killer of leaves comes from the attitude of going by arbitrary feeding regiments instead of learning how the plants grow and feeding them the food they need and when they need it.
But sitting at number one as the biggest killer of leaves is the 'panicky grower'. Growers who see something that is not quite cosher and in the reaction, over feed, over water, over foliar spray, over flush, in general over react and it is from this that plants suffer the most - add to that the number one worst environment for plants, plants sitting continuously in soggy soil.
