I have to concur with Lee. I don't use an afterbath and I mix up the "B" solution (6 gm sodium metaborate/liter) fresh each session and haven't had problems since. The following is a snipet of email I received from Carl Weese: "I think the number one culprit for bad PMK results is bad bottles of "B" solution, whoever/wherever they were mixed. After that, persistent
problems look to me more and more like water supply. And it might not
help to use distilled for the developer, because the water throughout
the process including wash is affecting the stain."

David, what did you mean by "has been extra edge density as a result of not using enough solution"? Total solution? I recently got a bunch of edge density (4 sheets 8x10/2 liters) but attributed to 1) trying a higher temp than normal and/or 2) they were doing lots of plumbing work in the building I rent darkroom space in and all sorts of stuff was coming out of the faucet. But now that I think about it, the best negatives I ever got was up at Carl's with fresh "B" and 3 liters/6 sheets.