from what ive seen a nitrogen deficiency can start at the tips and will eventually yellow the whole leaf, sometimes fairly quickly, sometimes not but have also seen most of the growth being very pale and the leaf turning yellow also, but it doesnt always appear that way and hes only 2 weeks into flowering.
there is really no such thing as a natural nitrogen deficiency it common to have the deficiency late in flowering but there is nothing natural about it, its a direct result of starving the plant of nitrogen in the last few weeks of flowering.