@ cutechuskay, just test with changing back to your old keywords and add only a few LSI keywords. @ cipals15, why did this happen? higher value per click or more clicks? I can not imagine that Google pays you more for the same number of clicks now that you are low traffic site.
could be a million reasons for this serps on a downward slide and an increase in PR. Linkage spam or even your competiion cranking up their SEO etc. Perhaps on the next google pagerank update you have completed a few tweaks in your keywords etc. good luck and hope your back up the rankings soon