Thanks all for the comments. I'm pretty confident the roots are getting air and not 'rotting' - mostly because I can see them and the bark is very loose. The plant after all isn't dying. It's just not growing.
The advice I'm getting is to change something and since we're coming into spring in Houston (which is similar to summer up north), I'll expose the plants to more sun (morning) and greater heat. We'll see if that changes anything. I'll also try Kelpmax as well.