I could not have used the fixer first. Twice I dumped 500ml of prewash liquid. I only have one container of diluted fixer-for-use (1000ml) and I am still using it. Also, stop, fix, wash and flo are located in a different area of the shop.
We are several people working in the shop and we have also been doing Cyanotype developed in 60ml vinegar per 1000ml water. The only explanation that I can think of, is that we somehow inadvertently polluted the diluted developer with vinegar. This, I assume, would be like a stop bath and probably kill the diluted weak developer before it was poured into the tanks for developing?
Anyway, I am sorry to have created a stir. Apologies. The main point is that there is nothing wrong with (my) DD-X.
On a separate note, I would assume that a prewash 'opens up' the film for developer rather than closing up the film. After all, fixer gets to the emulsion after short and long development times .....
Yes, Doug, I think that was the point in that particular Fred Picker newsletter. I will have to find that newsletter.