Add an inbound rule that allows all TCP traffic on all TCP ports. Set the security group as the source.

Add an inbound rule that allows all TCP traffic on all UDP ports. Set the private IP address of the RDS instance as the source.

Add an inbound rule that allows all TCP traffic on all TCP ports. Set the DNS name of the RDS instance as the source.

Replace the source of the existing SSH rule with the private IP address of the RDS instance. Create an outbound rule with the same source, destination, and protocol as the inbound SSH rule.