German balcony - Soil vs Hydro - Royal Jack Auto

After sprouting the seedlings looked quite sad. I suspect that the cocos pellets were far too wet, so I potted them the next day. The first plant is now in 15l of tomato gardening soil. The second plant is in a jar and dipping it's root into 300ml of Hydroponic solution. This will be a Kratky grow, but it will only enter it's final container with a higher nutrient level after growing a bit. On day 6 the plant in the soil became yellow at the edges of the leaves. The soil was dried up, so I did a good watering. That fixed the issue as far as I can tell. On day 8 the second pair of true leaves appeared in the soil plant and the root system visibly started developing in the hydroponic jar.