После переключения на nginx + php-fpm сразу же падает посещаемость сайта

Здравствуйте,

Хочу перевести сайт с nginx+apache+php(модуль Apache) на nginx+php-fpm, но после переключения сразу же падает онлайн, почти в два раза, видимо, посетители получают какую-то ошибку, но я не могу ее отследить. В логах ошибок сайта, пусто, а в access тоже ничего подозрительного, все стандартно, коды 301, 302 и 200 с положительной длиной ответа. Подскажите пожалуйста, как диагностировать проблему в таком случае, на что обратить внимание?

VPS сервер на VMware 1x2.4Ghz, 2GB RAM, 10GB SSD, Debian 8, ISPmanager 5 Lite, трафик 20.000 в сутки.

Онлайн по GA:

Статус Nginx:

Active connections: 489 
server accepts handled requests
 230680 230680 952506 
Reading: 0 Writing: 9 Waiting: 465 

Сайт работает на почти дефолтных настройках:

user www-data;
worker_processes  auto;
timer_resolution 100ms;
worker_rlimit_nofile 65000;
worker_priority -5;

error_log  /var/log/nginx/error.log warn;
pid        /var/run/nginx.pid;

events {
    worker_connections  1024;
    multi_accept on;
    use epoll;
}

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

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    #access_log  /var/log/nginx/access.log  main;
    access_log off;

    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    server_tokens off;
	
    proxy_buffers 8 16k;
    proxy_buffer_size 32k;
    
    server_names_hash_bucket_size       128;
    keepalive_timeout   30 15;
    send_timeout        30s;
    reset_timedout_connection   on;

    gzip_static  on;
    gzip on;
    gzip_disable "msie6";
    gzip_vary on;
    gzip_min_length 1000;
    gzip_proxied any;
    gzip_comp_level 4;
    gzip_buffers 16 8k;
    gzip_http_version 1.1;
    gzip_types text/css text/javascript text/xml text/plain text/x-component application/javascript application/json application/xml application/rss+xml font/truetype font/opentype application/vnd.ms-fontobject image/svg+xml;

    open_file_cache max=100000 inactive=40s; 
    open_file_cache_valid 60s; 
    open_file_cache_min_uses 2;
    open_file_cache_errors on;

    include /etc/nginx/conf.d/*.conf;
	include /etc/nginx/vhosts/*/*;
	server {
            server_name localhost;
    	    disable_symlinks if_not_owner;
    	    listen 80;
    	    include /etc/nginx/vhosts-includes/*.conf;
    	    location @fallback {
    		error_log /dev/null crit;
    		proxy_pass http://127.0.0.1:8080;
    		proxy_redirect http://127.0.0.1:8080 /;
    		proxy_set_header Host $host;
    		proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    		proxy_set_header X-Forwarded-Proto $scheme;
    		access_log off ;
    	    }
	}
}

C Apache:

server {
	server_name site.com www.site.com;
	charset UTF-8;
	disable_symlinks if_not_owner from=$root_path;
	index index.php index.html;
	root $root_path;
	set $root_path /var/www/site/data/www/site.com;
	error_log /var/www/httpd-logs/site.com.error.log notice;
	include /etc/nginx/vhosts-includes/*.conf;
	location / {
		location ~* ^.+\.(jpg|jpeg|gif|png|svg|js|css|mp3|ogg|mpe?g|avi|zip|gz|bz2?|rar|swf)$ {
			try_files $uri $uri/ @fallback;
			expires max;
		}
		location / {
			try_files /does_not_exists @fallback;
		}
		location ~ [^/]\.ph(p\d*|tml)$ {
			try_files /does_not_exists @fallback;
		}
	}
	location @fallback {
		proxy_pass http://127.0.0.1:8080;
		proxy_redirect http://127.0.0.1:8080 /;
		proxy_set_header Host $host;
		proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
		proxy_set_header X-Forwarded-Proto $scheme;
		access_log off ;
		add_header Vary "User-Agent";
	}
	ssi on;
	access_log off ;
	listen ip:80;
}

С php-fpm:

server {
	server_name site.com www.site.com;
	charset UTF-8;
	disable_symlinks if_not_owner from=$root_path;
	index index.php;
	error_page 404 /404.php;
	root $root_path;
	set $root_path /var/www/site/data/www/site.com;
	access_log /var/www/httpd-logs/site.com.access.log ;
	error_log /var/www/httpd-logs/site.com.error.log notice;
	include /etc/nginx/vhosts-includes/*.conf;
	location / {
		location ~ [^/]\.ph(p\d*|tml)$ {
			try_files /does_not_exists @php;
		}
	}
	location @php {
		fastcgi_index index.php;
		fastcgi_param PHP_ADMIN_VALUE "sendmail_path = /usr/sbin/sendmail -t -i -f admin@site.com";
		fastcgi_pass unix:/var/www/php-fpm/site.sock;
		fastcgi_split_path_info ^((?U).+\.ph(?:p\d*|tml))(/?.+)$;
		try_files $uri =404;
		include fastcgi_params;
		add_header Vary "User-Agent";
	}
	location ~* \.(js|css|png|jpg|jpeg|gif|ico|eot|ttf|swf|woff)$ {
        expires max;
        log_not_found off;
        access_log off;
    }
	location ~ /\. {
        deny all;
        return 404;
    }
	ssi on;
	listen ip:80;
}

Настройки пула fpm:

pm = dynamic
pm.start_servers = 5
pm.min_spare_servers = 3
pm.max_children = 15
pm.max_spare_servers = 5