I am totally new to this proxy stuff so bear with me and may not be using the right terminology

We have setup a proxy to our ec2 instance where we have a few dokku/docker containers that are hosting a few apps. the url for those apps are:
http://foo.dokku.abc.domain.com
http://bar.dokku.abc.domain.com

We would like to be able to have users only type:
http://foo.abc.domain.com
http://bar.abc.domain.com

we've setup a rewrite for the above urls which works fine.
http://foo.abc.domain.com -> http://foo.dokku.abc.domain.com
http://bar.abc.domain.com -> http://bar.dokku.abc.domain.com

however we would like it to not actually rewrite the url, we'd like it to preserve the url in the browser.

What can we do to fix this?

thanks

below is the code in /etc/nginx/sites-available/default

server {
        listen 80 ;

        server_name .dokku.abc.domain.com;

        location / {
                proxy_pass http://ip-aaa-bbb-ccc-ddd.us-west-1.compute.internal:80;
                proxy_set_header Host $host;
                proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        }
}

server {
        listen 80 ;

        server_name foo.abc.domain.com;
        rewrite ^(.*) http://foo.dokku.abc.domain.com;
}
server {
        listen 80 ;

        server_name bar.abc.domain.com;
        rewrite ^(.*) http://bar.dokku.abc.domain.com;
}