I'm building my own tile server with database on Amazon RDS and rendering it on AWS EC2. I followed this https://github.com/s6o/aws-osm-rds to do so. When I access the link http://your-ec2-dashed-ip-zone.compute.amazonaws.com/osm_tiles/0/0/0.png I get a blank blue tile. My guess is modtile is not able to access my DB. In the tutorial the only place where I mention my RDS db details is in osm2pgsql, is there anywhere else I would have to mention the data base credentials?