Yelllow leaves on 2 week old plants

i am a first time grower. On a few of my plants. the original 2 leaves that grow opposite each other in the first few days of the grow, are turning yellow a bit. the next set of three leaves look green and healthy. I need some advice or tips on what could be going on. i am growing 6 plants under 5 120 watt floros.

Needs nitrogen and or a transplant. As plants age bottom leaves fall off naturally but at 2 weeks it shouldn't happen. When I had this problem back in the day I figured out my girls just loved nitrogen =]