Too early to fertilize. They already have to deal with the nutrient charge in your soil mixture which is probably slowing their growth. Also, one litre per plant every three days? Do they look like they could drink that much? Did you plant them in the 5 gal. pots already? You get faster growth from seedlings and better control over their watering if you start in a small container and repot when they get some roots and a few sets of leaves.
Oh yeah, get a camera that can focus on your subject.