[Mon Aug 19 15:01:55.242179 2013] [:error] [pid 412:tid 2997121103616] (104)Connection reset by peer: [client 2001:4b98:x:x:x] FastCGI: failed to read from backend server

This error indicates that the Apache service did not get a response from the interpreter (PHP, node.js, Python, etc.) and so it was unable to deliver the requested page. When this error occurs, you should analyze the interpreter's logs in order to search for the error that is at the origin of the problem. To find the corresponding logs, it is recommended that you get the information from the date and time in the logs.