I bought two containers of sweet basil from a local organic market. One container had 3 sweet basils and the other had 2. I transplanted 3 basils into one pot and 2 on another. Now I'm seeing some browning from the stem nearest to the soil on ALL my basil plants. How can I identify whether it is rootbound or fusarium wilt?

Before I transplanted it, I tried to remove as much rootbound-ness as possible but it was too hard as the potting medium used by the seller was coco husks and it was very fibrous. I did not know this until I cut open the container to see the coco husks intertwining with the roots. I removed one plant and saw that I can 'skin off' some of the brown off the stem and it has new green stem. But I'm not sure if that's even allowed or safe for the plant.