Your roots look good to me, not an excessive buildup in the pot by any means, they're also looking very white and healthy, not yellowed or slimy or sickly. I saw you mentioned giving the boost of calmag, but just as an added thought kelp/seaweed extract is great for roots and any sort of potassium silicate will help strengthen the plants immunity and stalks. With the air pots, the great thing with those is they're constantly air pruning the roots, and whenever a root is severed new tiny fibrous roots fill in and their ability to take in moisture/nutrients is impeccable, I'm guessing because theyre so new and young. I think this is why there's usually a buildup of roots near the sides of the air pot and the drainage holes of regular pots because of the access to air.
Great growth in the last week, βοΈ