Somewhere I remember a mention that a "more-modern" technique in brewing meads involves a regular schedule of adding yeast nutrients while in the primary. I was never able to find the reference again and have so far been unable to find another source.
I know honey itself does not contain the ideal amounts of nutrients for the yeast (ignoring and fruit, spices, or other items I may also add to the must). When should I add yeast nutrients and how much to add?