nutrients?

i have had my babies out for 12 days now, they look good but could be better, what kind of nutrients should i be useing right now and for how long? should i use one now and switch to a different one later down the road? new at this so any info would help. thanks

listen mate jus stick to same nutrient try a light concentration then go on heavier when its a bit bigger. u want a food with lots of nitrogen