Elastic Beanstalk app won't connect to RDS MySQL instance

I have a CodeIgniter PHP app setup on an Elastic Beanstalk instance. I'm trying to connect it to a RDS MySQL instance I setup but loading the Elastic Beanstalk site URL always results in the page timing out the connection. I've narrowed down the issue to not being able to connect to the database.

I think I've setup my security groups properly to allow the Elastic Beanstalk EC2 instances to talk to RDS, but something must be wrong as the page still doesn't load.

I've included screenshots below of the inbound/outbound rules for the security group that RDS and Elastic Beanstalk use, as well as a screenshot of what security groups I have attached to the Elastic Beanstalk instance.

Any ideas as to why my Elastic Beanstalk app can't talk to my RDS instance?

EDIT: The RDS instance and the Elastic Beanstalk instance are in the same security group.