I used one of your formulas and the aforementioned Chinese amidol. As stated above, I suspect the impurities in that amidol were the cause of much (if not all) of the staining. They could also have affected the life, although there are many reports from the time of amidol's heyday that suggest a life of about 3 - 4 hours in tray. My experience was in the 4 hour range. I have used practical grade amidol in the distant past for things other than developers, and it was clean and very well behaved.
Originally Posted by Michael A. Smith