Website invisible for spiders but load great in the browser

Hello, I have very strange problem, some of my websites are not showing in the "seo browsers"(for example browseo dot net) but load normal in the every browser. That caused the first site to be deindexed from google and other one to be very low in SERP.
I host 4 websites in 1 server with same configuration under nginx + php-fpm . 2 of them are working great and have nice traffic.
The error log does not show anything after I use the "seobrowser" and the access log show my visit only with 200 OK code.Please for help before I go really crazy :S





p.s. I hope I'm in the correct forum category if not please move it.

Have you tried the Google Crawler? Is on the webmaster tools, and it actually gives you the raw output of their crawler. If I where you, I will start there. Remember now days anything gets tagged with the magic 3 letters "SEO" just to give it bang even is not useful.

Google Crawler works with no issues, but other spiders not. Also I got Response Code:502 in the facebook debugger when I put ANY link in the field. I thing those 2 things are related.