As for nutrients. What will they live on if i dont feed um? There is no goodness in rockwell and as soon as the roots are big enough they are going in the nft system for some serious growing time.
You can start giving them a LIGHT feeding at about 3-4 weeks. Then if they seem to be taking to that after another week or two then start increasing the fert. At seedling stage there's more danger in over-feeding than under-feeding. And most new growers tend to over-feed and over-water.

Dboy