Spotting

It's been a busy week, thus the brief hiatus in posting.

My wife started spotting last night, a full 5 days before she normally does. It was described as "brown" in color ... I'm no expert on spotting since I've never done it, but this strikes me a bit odd. My wife's spotting normally begins the day before she starts "flow", so this one being 5 days before the end of her normally very precise cycles is strange (she's usually at 25 days, exactly, to the hour almost)

I always chalk spotting up to "implantation bleeding", but have never been accurate in this assessment. Maybe this month is different? Doubtful, but it has to happen some time - right?