@bdilgard: Thanks for the reply, I certainly thought there would be more responses since so many here are anti-blix.
The Freestyle kit has no MSDS available to compare ingredients, I see. Bummer. Is it possible that, like the Unicolor kit, the bleach is labeled Part A, and the fixer, Part B? If you didn't catch that and just assumed Part A came first, well that would sure give the results you got!
Looking at my Unicolor K2 in more detail, I see that the fixer, besides the ammonium thiosulfate, has 5-10% potassium carbonate. That's a LOT of alkali for any fixer. And I see nothing in Part B, the bleach, that offsets that. Maybe I'll take tiny bit of the components and measure the pH, then mix, and measure again.
The digibase kit uses very different ingredients, ones that I have zero familiarity with, for the "bleacher" and the "fixer." But the pH for the latter is an expected 6.2, IIRC.
Tis a puzzle.