Being that I'm not familiar with that
growing medium, nor can I actually feel it for dampness, I just cant say if your over watering or not. I think your system is the one with a tube running through the square tubing to spray water on the baskets/roots, but again without being familiar with that growing medium, and not being able to feel the growing medium. I just cant tell how saturated it is. Though I have a couple of questions:
1. How strong is your
nutrient solution?
2. What is the air temp?
3. What is the nutrient solution temp?
4. Are you covering the seedling to keep in humidity?
5. What is the plant/s (lettuce)?