Great news.

Yeah, that method of filling up the tubs should accomplish the same thing for hydration, good work.

I wish I could've seen more pics of those roots. But if they really were tan, not dry/brittle, and I did see a few white tips also, then Millet is probably right and the root ball is doing fine.

It was probably just under watering, or "adjustments" due to the Air-pots.

Like I said, my trees have die-back during the first few months when placed in the Smart pots (I assume they are losing roots due to the outer 2 inches or so drying out quickly with black cloth). They always do better when I put them into a larger pot (protect from direct heat/light) and then put bark around the gaps (help insulate better).

It's all a learning experience and requires adjustment for each pot, media, and micro-climate.

If your third tree is still in the original pot, I would use a cache pot around it until next Feb.

Good luck