You did not put the empty reel on bottom and full reel on top. I put 2 reels in full, and only enough solution to cover bottom. (By mistake, before I measured how much solution I needed). Top reel developed to the same extent the bottom did. Kind of an extreme compensation technique?(posted 8493 days ago)You might not have had full density had you done this, but most assuredly the top would have shown decent, perhaps compressed, images.
Best estimate is the Dreaded Xtol Failure.