The sheets I processed this morning are just backups of other mediocre setups (probably why they were never processed: why yawn twice?).
In one envelope, I found two sheets that are basically glued together. I have them soaking in a warm bath now, but I have little hope for them: the run-off from the first rinse was gray. ☹️
Okay, so the two sheets that were stuck together were unrecoverable, as feared. Of the other four: two were blank, and two were photos of an antique store that came up in conversation just yesterday. (😳)