yeh dont nute seedlings, cuttings are a bit more hardy although you wouldnt nute them too much either. although I say that here and have two cuttings in the same nutes as my older clones but even then I never nute them too much 250 [email protected] conversion, as long as the water never gets below the starting ppm of 60, i dont give a fuck.
even as Zan says, the third leavews, but even then be very careful, my tap water is 60 ppm, at the third leaf stage I wouldnt go past 100 ppm, but that can be strain and climate specific, I grow in a hot area most of the year round