Looks like a root issue. My guess is drainage is impaired in some way…. Broken down media, clogged drain holes
Might want to pull the whole shooting match out of the pot and check the media… and drain holes. Could possibly drill the media with a long 1/“ drill (let the drill go where it wants to). Or better still… drill holes all up and down and around the side and bottom of the nursery pot.
We do this a lot to help drainage and root prune when no baskets are on hand.
Other ideas. Remove 1” of the bottom media and add a 1” layer of pumice on bottom to help drain the pot.
Finally put a 2x2 or rock under one side of the pot to lower the water table and help drainage.
Good luck!
DSD sends