mhansen - 6:51 pm on Oct 21, 2012 (gmt 0)
@ Nichita -
I would take it a step farther and suggest you find all common traits about your sites.
- Same server?
- Same Whois account owner?
- Same Webmaster Tools account?
- Same backend technology? (like wordpress or other CMS)
- Same Adsense or other ad network?
- Same look and feel or theme?
- Same niche market?
- Same type of site (articles, blogs, buying guides, ecommerce, etc)
I would make a list of everything my sites had in common, and use that in determining what else could be wrong as well.