Exam AWS Certified Solutions Architect - Professional topic 1 question 835 discussion

A company has multiple AWS accounts as part of an organization created with AWS Organizations. Each account has a VPC in the us-east-2 Region and is used for either production or development workloads. Amazon EC2 instances across production accounts need to communicate with each other, and EC2 instances across development accounts need to communicate with each other, but production and development instances should not be able to communicate with each other.
To facilitate connectivity, the company created a common network account. The company used AWS Transit Gateway to create a transit gateway in the us-east-2
Region in the network account and shared the transit gateway with the entire organization by using AWS Resource Access Manager. Network administrators then attached VPCs in each account to the transit gateway, after which the EC2 instances were able to communicate across accounts. However, production and development accounts were also able to communicate with one another.
Which set of steps should a solutions architect take to ensure production traffic and development traffic are completely isolated?