ur plants are too young to nute. wait until they enter flowering if ur doing around 4 wks of veg. it really depends on the size of the pot ur using. i use like a 15-20 gal bucket and started added nutes in week 3 of flowering after 5wks of veg. i just use some Earth Juice Bloom every other watering (i water every other day now) and flush once a week. go organic for good taste.