Can use different certificates on backends, each with a different server_name

I currently have one load balancer and four backends server configured to proxy_pass several subdomains under one domain using https protocol.
The ssl certificate for this domains are all defined on the Load balancer and the backend server. I believe the load balancer is the one serving the certificate due to the fact that once i remove certificates entries from it my sites stops working.

Currently the system is working fine my challenge now is that I need to add another domain with its own certificate. My nginx.conf on the loader balancer where I declared upstream servers does not allow me to add another block. The moment I try adding the block I get errors. I have attached my nginx.conf of the load balancer.

I have configured ssl for the new domain on the backends but the moment I browse the domain it gets the certificate of the first domain possible becoz its not declared on the load balancer. My question is how can achieve this scenario. I have attached my nginx.conf the commented lines indicate lines which were making nginx fail.

I am still a learning Nginx if you can kindly check my configures and assist.