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They look like they need to be moved into larger containers. Chestnuts are large trees and will need to be accommodated for growth. They also need acidic soil which they may not have. When you upsize, mix the soil with about 1/2 sphagnum peat moss and 1/2 potting soil. You also can buy fertilizers for acidic plants that will help.

Brown edges also can indicate too much or too little water. Increasing the amount of soil will help with water retention.

They will need a dormancy to remain healthy. For dormancy of an American chestnut tree in a container, follow these steps: Begin by choosing a suitable container with drainage holes to prevent waterlogging. Fill the container with a well-draining soil mix. Place the American chestnut sapling in the container, ensuring its roots are adequately covered with soil. Water the tree thoroughly and place the container in a cool cellar with a temperature between 32-40°F (0-4°C). Monitor the soil moisture regularly to avoid excessive dryness. During dormancy, limit watering to prevent root rot. Check the tree for any signs of pests or diseases, and apply appropriate treatments if needed. When it's time for planting, gradually reintroduce the tree to warmer temperatures, acclimating it to the outdoor environment before transplanting.

Here is an article for more information on care for your tree:

https://www.gardeningknowhow.com/edible/nut-trees/chestnut-trees/american-chestnut-trees.htm