tbm said:
My decision to process Acros 100 at ISO 200 in FX-50 was based on Paterson's FX-50 PDF file, a screen capture of which is attached, and I used the development time Crawley recommends. The flatness of my processed film was clearly based on a problem with the quality of the liquid in the package I had, not on the processing time. Again, perhaps the bottles in the package B&H previously sent me had sat on their shelves for a phenomenally long time and had oxidized to some extent, whereas perhaps this does not occur as much in photo stores in England. I don't know for sure, of course. Crawley is a genius in the photography world and his recommendation on the attached page can certainly be trusted. Perhaps if, upon receiving the previous package of FX-50, I had immediately transferred it to two small amber glass bottles I wouldn't have experienced the processing failure. Again, I don't know.
I have always been skeptical of claims for speed increasing developers. Most films do not give the claimed ISO speed in real world shooting conditions.This also applies to films souped in standard developers. This is due to all kinds of variables that can not be accounted for in a laboratory test, (too expensive for the manufacturer). Little things like differences in shutter speeds, light meters, processing conditions, enlarger light source, etc. can have a big effect on your results.
The way I would approach it, after having a temper tantrum because the film didn't come out as hoped for

, would be to reshoot the film at a range of exposures from EI 40 to EI 160 and develop the film at the same time and temp as the previous roll. Only change one variable at a time. This should give you some denser negs, especially at the lower end of the film speed scale. You should then be able to try printing some of them to see if you're getting enough shadow detail. If you're getting shadow detail, but the contrast is still flat, try shooting a third roll, at the lower speeds, and increase your your developing time by 25% or more. For Acros, your new time would 11 minutes and 15 seconds, using a 25% increase. It is better practice to think in terms of of percentage increases or reductions in your developer times rather than adding or subtracting a "minute or two".
What kind of light source do you have on your enlarger? If you have a condenser unit, the negs might not print a flat as their appearance on the lightbox may suggest. When I stopped printing my 35mm negs on a diffusion enlarger, I had to cut my dev times way back to get the contrast I wanted on my preferred paper with a condenser enlarger. I ended up diluting the developer more so the time would not be too short. I like my dev times to be in the 7.5 to 11 minute range.
Crawley is a genius when it comes to photochemistry, but even geniuses are not infallible. He also probably uses testing methods that are vastly different from anything you or I would use. Remember, he is working for a company that is selling his formulas, and therefore may be slightly biased in his opinions regarding this formula. He may also be making dev time recommendations for condenser enlargers. I believe that people in Europe are more likely to use condenser enlargers.
As you mention, storage conditions probably are a factor here. We don't know exactly how old the developer was by the time you received it. Maybe it just does not have the shelf life that other developers have. For this reason, I do not keep store bought liquid developer concentrates on hand for long periods of time. Except for HC-110 syrup or Rodinal, I try to use up any developer concentrate I have within 1.5 months of purchase. I usually just make up my developers from scratch, mixing up only as much as I think I'll need for 1 or 2 weeks. It seems to be less wasteful.
I know that you like Delta 100 souped in Microdol-X diluted 1+3. Have tried souping the Acros with that setup? It might be just what you're looking for. At least it would be easier to compare differences in the behavior of these two films if you are using the same developer for both. Just make sure that the Acros and the Delta are not developed together.
After looking up all kinds of stuff about FX-50, I notice that there is a wide range of opinions of it. Some folks think it's great, some think it's a dog. I haven't used it myself, so I have no opinion. Apparently this developer is subject to sudden death syndrome just like Xtol. At this point in time I am leery of any commercially prepared developer containing Vitamin C. Too many shelf life issues. I have played around with Pat Gainer's formulas, some of them look promising, and they are dirt cheap.
GTF