Leaves help

This is quite typical for a plant that is flowering. Giving "grow" nutrients, say half strength combined with half strength "bloom" nutrients during the first 2-4 weeks of flowering can be beneficial, as cannabis still needs adequate nitrogen early in flowering. Also, cannabis, being the "Super Smart" plant that it is, will actually re-use elements that are "stored" in the older leaves, almost like a warehouse of vital elements, such as carbs, amino acids, sugars etc, that she draws upon when flowering. It is far more efficient for her to re-use the "stored elements" in her leaves as it is to grow flowers and have to make new carbs, amino acids, sugars etc at the same time when energy usage should be going into flower production - which after all, is her prime objective in life, growing flowers to make seeds and ensure the survival of her species. It is also fortunate that you have not defoliated your plant, otherwise this rich bounty of stored elements would not be available to her; apart from leaf removal also limiting her ability to produce energy, two things advocates of defoliation fail to understand, and two of the most needed things during flowering. Or to put it another way,.... Maximum leaves = maximum energy production = maximum reserves of vital growth elements = maximum growth/flower size. Due to the plant re-using the elements from her older leaves, it will cause the older leaves to go yellow during late flowering and is a natural process. Hope this helps,.... Organoman.