Article Directories Ranking Increase?

I just checked my two main keywords and saw that the articles from articledirectories has taken the top 3 spots again.

Is this just for my keyword or are have all their rankings increased?

*Fortunally most of those articles are linking to my page

What would be the reason for such an event?

Are we talking about an article directory that previously had low ratings and is now suddenly rating high? Or are you talking about some other scenario?