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I have a website that we look after, up until January this year the rankings were really strong - the site has a much higher domain authority than the competitors, much more links and much more relevant content (all measured with moz's tools). About 6 months ago the rankings started to dive for national search terms. Now one thing ive noticed is that nearly all of the other sites in the search sell products online where we have no such function - could this be correlated - has anyone else experienced this?