Is there Data tied to VPC / Subnets? (No RDS/Instances/Snapshots)

Hello, We are reviewing our AWS account and found that we have a RDS and EC2 running that are incurring costs but we don't know what they are being used for. Investigating further, it seems as there is no information in the RDS (no DB instances or snapshots) or in the EC2. We can only find the VPC, Parameter Group and Subnets associated. How do we go about doing the following?:

1. Finding out if there is any information actually tied to these groups? These two things (RDS/EC2) are the only thing on the East Ohio server for us.
2. If there is no information tied to them, how to go about deleting?
3. Out of curiosity, how could this have been generated if a DB instances was not associated with it?

Any help/advice would be greatly appreciated!

RDS Screenshot - Only Parameter Group/Subnet:

EC2 Screenshot - Only Security Groups (VPC/Subnets):