There are continuous manipulations in the Page Rank algorithms of Google.Google changes the ranking positions of search results on a continuous basis just to know user's behavior.This helps them come up with the best results depending on user satisfaction.
So,there's nothing to worry as of yet.Review your posts once again for quality and unnecessary use of keywords.And as Mani has said,concentrate on hot topics that can bring good traffic to your site.
And coming to money,it's not all that easy to make 25$ a day.That requires your blog to have a wide variety of posts at good SERPs.In my opinion,your blog needs a lot more content and approx. 15-20K impressions per day to reach that mark.All the best..:)
http://www.sitegorge.com