Hum ? Reading other stuff from people who know about these things, I understand that at that stage the yeast might have trouble absorbing inorganic nitrogen sources (and I see little point in adding something that could cause off flavours or leave too much available to spoilage organisms....if they go in) I'd suggest maybe some FermaidO (if you can get some) or boiled bread yeast or yeast hulls i.e. an organic nitrogen source.
"What the large print giveth, the small print taketh away". Tom Waits.