502 Bad Gateway, upstream prematurely closed.

There is an error on two pages. How can i fix 502 Bad Gateway? Thanks for help. Have a nice day… http://luxger.com/galeri/motif - 502 error, 178 images http://luxger.com/galeri/gokyuzu - 502 error, 131 images http://luxger.com/galeri/gokyuzu-agac-cicek - no Error, 286 images Nginx Error log:

...upstream prematurely closed connection while reading response header from upstream, client: 84.104.247.91, server: www.luxgergitavan.com, request: "GET /galeri/motif HTTP/1.1",... 

File: /etc/nginx/nginx.conf

worker_processes 4;
pid /run/nginx.pid;

events {
	worker_connections 768;
}
http {

	##
	# Basic Settings
	##
	sendfile on;
	tcp_nopush on;
	tcp_nodelay on;
	keepalive_timeout 65;
	types_hash_max_size 2048;

	server_names_hash_bucket_size 128;

	include /etc/nginx/mime.types;
	default_type application/octet-stream;

	##
	# Logging Settings
	##

	access_log /var/log/nginx/access.log;
	error_log /var/log/nginx/error.log warn;

	##
	# Gzip Settings
	##

	gzip on;
	gzip_disable "msie6";

	##
	# Virtual Host Configs
	##

	include /etc/nginx/conf.d/*.conf;
	include /etc/nginx/sites-available/*;

}

File: /etc/nginx/sites-available/luxger.com

upstream luxger_app_server {
   server unix:/var/www/luxger.com/run/gunicorn.sock fail_timeout=0;

}

server {
        listen 80;
        #listen [::]:80 default_server ipv6only=on;
        client_max_body_size 4G;
        sendfile on;
        keepalive_timeout 0;
        large_client_header_buffers 8 32k;

        root /var/www/luxger.com/;

        server_name www.luxgergitavan.com luxgergitavan.com luxger.com www.luxger.com;

        access_log /var/www/luxger.com/logs/nginx-access.log;
        error_log /var/www/luxger.com/logs/nginx-error.log;

    keepalive_timeout 0;
    large_client_header_buffers 8 32k;

    location /static/ {
        alias   /var/www/luxger.com/static/;
    }

    location /media/ {
        alias   /var/www/luxger.com/media/;
    }

    location /static/admin {
        alias   /var/www/luxger.com/static/admin/;
    }

        location / {
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_redirect off;
                proxy_buffers 8 32k;
        proxy_buffer_size 64k;
        if (!-f $request_filename) {
            proxy_pass http://luxger_app_server;
            break;
        }


        }
        #error_page 404 /404.html;

        # redirect server error pages to the static page /50x.html
        #
        #error_page 500 502 503 504 /50x.html;
        #location = /50x.html {
        #       root /usr/share/nginx/html;
        #}
}