Your containers are designed to protect the longer root development. Your container does not promote oxygen getting to the roots which is a major issue in my opinion. If you can add some ventilation holes that will help with the oxygen. Your pictures helped greatly. My labs got me up in the middle of the night so the first time I looked at them I was half awake.
Your photo were too large in size to load on this forum. Your seedlings are going to do fine but you need to address some issues.
1. I like the color of the leaves - they look healthy and the right color of green. You don't have scaffolds of leaves and your stems are too long and leggy. The light source is weak and too far way from the top of the stems - Therefore - they reach for the sun / energy. Rearrange the containers by height. Get your lights closer to chestnuts that have not germinated. Get your light closer to the seedlings that are leggy.
2. You need to feed the seedlings that are leggy. You will feed them by directly watering that container. I will show you a photo of what to buy at Walmart, Lowes or show other store. It is a water soluble fertilizer for "Acid Loving Plants". It will provide some nutrients that the new growth needs.
3. I suggest you add some Osmocote Plus - a slow release fertilizer to the leggy ones also. It don't give you an immediate dose. I would mix it in the top inch to inch and half of growing media.
4. Chestnuts can get big leaves and weak stems to the point they will not hold themself up. I was shocked at how stemmy they are.
5. How do you know the dripping system works equally across the containers? Is it possible that containers closer to the supply of water get more than they future down the distribution system. I ask because I have no experience with this approach to watering.
6. I personally like 12 to 14 hours of light and 10 to 12 hours of dark. You can't run light on those seedlings constantly. I get busy and forget therefore, I use a timer to control when lights turn on and off.
What is normal? Nature claims the weak - only the strong survive. If you have 50 germinate and grow one scaffold of leaves - some of those 50 will die off regardless of what you do. I pray they die on your while they are growing in the bathroom as opposed to after you plant them in their field location. Loss of part of the process. You are going to be plant plenty of dunstan chestnuts.
Four photos I am posting 1) Water Soluble Fertilizer, 2) Osmocote Plus and 3) Some Chestnuts that Scaffolds of Leaves When Lights Have Been Maintained at correct distance. My containers are rootmaker 18 express. 4) How seedlings look when they lights are maintained at correct distance. Two trays sunning on car hood.
Congratulations - you are going to wind up with many chestnut seedlings based upon this beginning. The devil is in the details.
In the photo of seedlings - notice the color and multiple level of leaves on a stem. The photo above is where the seedlings are older than yours currently are. The photo below shows how seedlings looking after they are ready to move from smaller containers to larger containers or field planting locations. I am introducing the seedlings to the sun on a car hood to discourage rabbits and squirrels from messing with them. My lights are adjustable height wise which is very important to prevent the seedlings from reach upward for the energy and getting top heavy.