Matt,
the only time I experienced that kind of fog was with RC paper - it resulted in a pink stain in the white borders.

What happens is that development continues in the fix, fix and dev work against each other - my best guess is that the desensitizing or sensitizing dyes are responsible for the tone. But I have heard that it happened on film, too, there was a sample posted at photo.net a while ago.

The guy ended up with partially pink casted negatives that might influence the print in the way a staining mask does - imagine a evenly toned texture, partially stained and thus showing differences in the tones on the print.

But you are probably safe - you let the developing agents do their work on the emulsion and "die" before putting the negative in the fix.