Applications all down at the same time

The GAS is probably down. You can find some clues in:

GAS logs
Web server logs

One reason could be a cron or a script that periodically shuts down and restarts the web server. For example, in the Apache log_error file you can find messages like:

... [notice] SIGUSR1 received.  Doing graceful restart
... [error] [client xx] (4)Interrupted system call: FastCGI: comm with 
server "/opt/gas/bin/wrapper.fcgi" aborted: poll() failed
... [error] [client xx] FastCGI: incomplete headers (0 bytes) received 
from server "/opt/gas/bin/wrapper.fcgi"

Apache received a SIGUSR1 signal. If you search through the error_log, you might have the message daily at the same hour. This is probably due to logrotate (see /etc/logrotate.d).

In order to archive the logs, logrotate asks Apache to restart gracefully, so it shuts down the fastcgi, the dispatcher and all Genero applications. You can check if it is really the culprit by using this command (or an equivalent one):

/etc/cron.daily/logrotate --force /etc/logrotate.d/apache2

To solve, amend your logrotate to process when Apache stops, or at night, or save the logs of the previous day so that you can archive the logs without stopping Apache.