Um the oringinal post sounds a lot like undissolved fixer contaimination.
Viradon is very picky on clean prints , found this out the hard way when I tried to hide a stain caused by a faulty drying rack.
The viradon really drew attention around the rust stain. also after that I figured to try something by dipping the print into an old(luckly) fixer solution... this caused fizz for a bit and uneven tonality as if that really mattered anyways.
Another print showed a small gain in latent highlight detail after toning. so its got my vote for future use.