[AlaninCarlisle]

Rather than mess around making various "brews" of nettles etc, I've just used bog-standard (12:3:9 with added Fe and Mg) grass fertiliser that was left over from last year. Leeks still swelling but the ones I planted in May are nearly two inches diameter already

[Trillium]

Leeks can't read so they don't know the difference 

[AlaninCarlisle]

I figured that all the traditional brewed "black-art, foul-smelling pick-me-ups" that the old guys use are just different ways of hi-dosing them with nitrogen as the other essentials they'll pick up from the soil

[Salmo]

Nitrogen is what grows leeks.

There is one thing, with the Fe you should not get any trouble with moss around the leeks.