I've had #1 rankings for a while for some of these sites and many page 1 rankings. Today I noticed the #1 ranked sites moved all the way to #5 and others from page 1 moved to pages 3-5. I have not done anything to these sites for some time. Is it a change in the algo that affected my sites cuz I can't believe it's the competition since many of these are store sites that are not even optimized for the keywords, but have moved ahead of me. Any suggestions? Should I start building links again to these sites to move them up or what?