In some of the earlier pics, the soil looks moist. In the last pics, it looks to me like the soil is peat moss, or similar, and looks very dry. It probably drains too easily and dries out quickly and it would appear to me that the plants are looking as if they are suffering from dehydration, ie not enough water.
To help remedy that, place a tray under the pots and water the tray. Let the soil in the pots absorb the water until the soil is wet. When the soil is 'wet', drain all excess water out of the tray. At this early stage in the plants lives, nutrient deficiencies would not be a factor...but some mild fert will help them along nicely.
