So this is straight coco coir you are growing in (I notice you said GH brand)?
Coco coir tends to hold onto Ca and Mg a bit strongly. You might consider mixing in some dolomitic limestone before planting, or use more liquid Ca/Mg supplement, depending on your tap water source. New seedlings really don't require much, although coco coir itself doesn't have much nutritive value. One thing I notice from your pictures is that you leave a lot of extra space at the top of the container. Fill it up entirely, so the roots have more space to grow.
I also notice some stretch, keep the light closer and make sure you have adequate circulation. CFLs should be within several inches of the plants.