Fletch

Pine's roots do tend to go deep if they can, the best way I've found to get better growth throughout the pot is to spread the roots out radially when repotting. I even tried placing a tile under the tree to block them once but really didn't get much better results than just spreading them out, you might also try using a shallower, wider pot as a training pot or maybe even building a shallow grow box...BTW what are the dark blotches on your pot and in the needles in the third pic?

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Regards
Fletch