Well you shouldnt fertilize until they have 5 or 6 nodes, use it at half strength in a 2-liter soda bottle put 7-10 drops. fertilize every 2 feedings , then the third use straight water.

As they get bigger you can increase the fertilizer to full strength. Water when the soil feels mostly dry and/or container feels light. You can put your finger down in the soil to test the dryness. The urine is good for N , just dont overdo it with it. And you really should have waited till the plants were on the 4 or 6 node (nodes are the sets of leaves) to fertilize.

For some decent cheap soil go to walmart and get there "expert gardener perfect mix" like $2.50 a bag, Its got lime& pertlite already added and its got a
nice texture.
And there "expert garderner all purpose plant food (24-8-16)" is like $3.50 for a 1.5lb box of the water soluble powder,thats the vegg growth fertilizer I use.