Nginx loading page very slow

I just deployed nginx in a new environment with the same configuration that I've used previously and I am seeing some very odd behavior.

Nginx is configured as a reverse proxy for Solr, when I try to access the Solr UI through nginx, it takes about a minute to load. I checked Chrome dev tools and it looks like the browser is able to download 6 files right off the bat, however then all other requests are in a pending status. Then it just sits there for exactly a minute and after that everything gets downloaded and page loads. After that, the browsing is fast; I think this is mainly because of local browser cache.

Here is the config:

worker_processes  10;
error_log  /directory/path/error.log debug;
pid        /directory/path/nginx1.pid;

events {
     worker_connections  1024;
}

http {
 access_log  /directory/path/access.log;
 proxy_temp_path /directory/path/ 1 2;

upstream backend-test-old {
    server 1.1.1.1:7071;
    server 2.2.2.2:7071;
}

server {
    listen       7071;
    server_name  localhost;
    access_log /directory/path/access_7071.log;
    proxy_ignore_headers "Set-Cookie";
    proxy_hide_header "Set-Cookie";
    location /solr {
        proxy_pass http://backend-test-old;
    }
}
}

I also see a lot of these in the logs:

2015/07/10 11:06:38 [warn] 31503#0: *120 an upstream response is buffered to a temporary file /dir/path/7/00/0000000007 while reading upstream, client: 111.111.111.111
2015/07/10 11:06:36 [info] 31503#0: *96 client prematurely closed connection, so upstream connection is closed too while connecting to upstream, 
2015/07/10 11:06:36 [error] 31503#0: *101 upstream timed out (110: Connection timed out) while connecting to upstream, client:

Now this is not a problem on my dev server, which runs the same config and should be configured relatively similar, so it could be something system related, but I am not sure.

Any help would be much appreciated.

Thanks

EDIT:

It looks like the issue is me pointing to back end hosts by IP vs hostname. I am not sure why this is an issue. I've implemented this config:

worker_processes  10;
error_log  /path/error.log debug;
pid        /path/nginx1.pid;

events {
    worker_connections  1024;
}

http {
     access_log  /path/access.log;
     proxy_temp_path /pathproxy_temp/ 1 2;

    upstream backend-test-old {
        server hostname-for-1.1.1.1:7071;
        server hostname-for-2.2.2.2:7071;
    }

    upstream backend-test-old2 {
        server 1.1.1.1:7071;
        server 2.2.2.2:7071;
    }

    server {
        listen       7071;
        server_name  localhost;
        access_log /path/access_7071.log;
        proxy_ignore_headers "Set-Cookie";
        proxy_hide_header "Set-Cookie";
        location /solr {
                proxy_pass http://backend-test-old;
        }
    }

        server {
        listen       7072;
        server_name  localhost;
        access_log /path/access_7072.log;
        proxy_ignore_headers "Set-Cookie";
        proxy_hide_header "Set-Cookie";
        location /solr {
                proxy_pass http://backend-test-old2;
        }
    }
}

If I go through 7071 it works fine, however if I hit through 7072 the performance problem described above occurs. Does anyone have any ideas?