Just a thought have you tried to processing unexposed paper? This would tell you if it is something with the paper..it may seem wasteful but it would save the frustration of having to remake the image and if it is the paper perhaps you can determine if something happened to it or if it just a bad batch. Had something like this happen with Ilford, but did not show up until after the print was complete and then toned..keep us posted on what you find.