water them so the soil is moist , then you put them under your light and water when it starting to dry out if not moist 2 inch or 3 cm down you can water also ,sometimes it drys out quick sometimes not sorry my english hehe
soil if soil grown contain the nutrients to last weeks no need to feed really, its my opinion about soil ,In hydro and such an 0.5 ec would do . but we build our houses diffrent and gardens to just have fun :)