I bought the site freexboxlivegoldmembership.com from Flippa a week ago and since then the site suddenly lost Google ranking for some major traffic driving keywords. For example for the keywords "free xbox live" and "free xbox live gold" the site went from page 1 to page 40+. As a result, organic traffic dropped by more than 50%. At first I thought the site was sandboxed or slapped by Google Panda but what confuses me is the fact that it is still on first position for the main keyword "free xbox live gold membership". I did not do any backlink building since I bought the site and the site has been on page 1 for these keywords for many months until now. So what else could cause the SERP to drop so rapidly for some keywords but not for others? Should I request a refund from the seller?