ok... I'm probably wrong, but here's what I'm thinking... nitrogen is important in the vegging stage, quite obviously. giving nitro boosts to seedlings and clones (at the start) is advised against. I agree it would be advantages early on, I would go really weak at first, however. for clones, which is how I generally propegate, I just soak the peat pellets in a weak rooting solution, along with the rooting hormone on the cuttings (some samples I'm using up, and seems to work 'the cat's but').
once you got roots, then the nitrogen heavier ferts can be used - that's what I do... for my vegetables, I mean... :hubba:
and the thing about your apparent nitrogen dificiency... commercial potting soil is suppost to be just that... just soil - no nutes.
the reason the nitrogen is deficient for your levels, is cuz it is being used up the most by the plant, so therefor needs to be added.
k... i'm gunna stop talking now