They don't look terrible but don't seem to be thriving either. Hard to say but whenever I see plants that young already struggling, I think either to much water / incorrect watering or too much food. In this case I am leaning to water just by looking at them.
Water - When you water soak them good untill they drain completely. Then do not water again not even one little drop till that cup is almost completely dry and light. Waiting is especially important when you have a tiny plant in a fairly big cup. The drying process causes the roots to spread out seeking moisture and then it takes off when the water finally comes.
Food -
Have you given any fert yet? Was there any nutrients in the soil or was it sterile? Even with a fairly sterile mix, you can usually go bigger than that size before you even need to feed one time. Always go with a low dose the 1st time too.

Temps - Whats your overnight lows like there?