Help with sick plants ..

What type of soil are you using?
Have you fertilized them yet?
What is the soil ph?
What type of lights?

 

Yep, need more info to make it anything other than a wag (wild ass guess).

The cotyledons should discolor and die off. When that happens, that is when a lot of growers start to fertilize.

The way the leaves are pointing up, I am betting whatever light source you have is too close. Heat is getting to them.

But see the first sentence about WAGs. Lol

 

I think a little early for 10-18-10

 

oh boy, you may have burned them, never use nutrients before 2 weeks of age, those cotyldeons on the bottom part of the plant feed the plant enough food untill they get big enough, a weak dose of nutrients like 1/4 teaspoon for first feeding
and up the dose to 1/2 teaspoon per gallon for chemical nutrients and 1 tsp per galloon for most organic nutrients
plant should be bigger so there was either some problem with your seeds, or your seed mixture or you watered to much....
some kind of stress to stunt it

for those cotyldeons to yellow and plant not be bigger shows there was a problem.......

 

I agree with Stitch.
You fed the plants too early. The next time they are ready to be watered, flush them out. A flush consists of at least twice as much water as the size of the pots; 5 gallon pots, 10 gallons to flush. Also, I would put those CFL's a few inches closer to the plants. That one stretched up for light. Put them within 3 inches and monitor them closely. They should be fine that close as long as you have a fan.