[Plugin: WordPress SEO by Yoast] All posts add a prefix word 'tweet' in feeds

Somehow all my posts automatically add a prefix word ‘tweet’ in the feeds.

Feed URL – http://feeds.feedburner.com/cosmogeekinfo
Blog URL: http://iCosmoGeek.com

The prefix is viewable on the site in the page source (couple lines after feed autodiscovery tags) of individual stories.
( <meta property=”og:description” content=”Tweet … )

I remember I made some changes in SEO>RSS section (content to put in before and after each feed). I tried disabling the plugin as well but still all my feeds add a prefix word ‘tweet’.

Any help is highly appreciated.

http://wordpress.org/extend/plugins/wordpress-seo/