Yeah, I’ve discovered that my choice of fixer was not the best. Discussions online of fixers are few and far between compared to discussions of developers. It was not powdered, but it is non-rapid, hardening kodafix. Specifically this:
https://www.freestylephoto.biz/1464080-Kodak-Kodafix-1-Quart-(Makes-1-Gallon)
My first batch of fixer I dumped after about 6 rolls of 35mm over three weeks because when I tested with the Delta 100 it wouldn’t clear at all after 8 minutes. So I dumped the fixer and mixed up a new batch, tried another piece of the leader, and still nothing. The fixer was brand new before it was opened for that first batch, and has worked great for other rolls.
Now I don’t know the history of that Delta 100. Basically, I bought someone’s darkroom equipments, mostly for the Omega D2, but in all the stuff he had was also a bulk loader that was mostly full. There was a piece of tape on the outside that had a date from 1998. The first rolls I shot from that sort of worked (that’s how I figured it was Delta 100) but since then the next roll didn’t clear at all, and I haven’t used it since. I saw where all the gear, including the Delta was stored, and I wouldn’t be surprised if it spent 40-60 days every year in 120 degree temps or higher.
Again, thanks for the insights. I agree with pentaxuser that the actual cause will probably remain a mystery, but it good to know that I didn’t do anything obviously wrong. I suspect this process (film...) it to a large extent about developing consistency then adjusting consistent processes to get the results I want. I’m still new at this and I may have made mistakes I didn’t remember or even notice.