nginx.conf dosyasında şu düzenlemeyi dener misiniz;

server {
    listen 80;
    server_name xxx.com;

    location / {
        proxy_pass http://ana_sunucu_ip;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

    }

    location /blog/ {
        proxy_pass http://blog_sunucu_ip;

        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
}