Slow Mutlisite Performance

Dear all,

We have a multisite WordPress network that is based on SubFolders, and we’ve had some issues regarding the overall performance of the network.

The problem is that all the network sites have a very slow performance when they login, edit post, edit page, view themes, view plugins or any other activities.

We’ve tried to follow up the problem and we temporarily solved it by switching all sites to this theme: https://www.justskins.com/wordpress-themes/curved-wordpress-theme/22
and by also disabling functions.php on this theme. After this all the sites are working fast with no lag. But we need to enable users to choose themes and use them.

Here’s our htaccess file configuration:

# BEGIN WordPress
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# uploaded files
RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-includes/ms-files.php?file=$2 [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(wp-(content|admin|includes).*) $1 [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(.*\.php)$ $1 [L]
RewriteRule . index.php [L]
# END WordPress

AddType application/octet-stream .rar

<IfModule mod_security.c>
<Files async-upload.php>
SecFilterEngine Off
SecFilterScanPOST Off
</Files>
</IfModule>

Our base URL is sites.iugaza.edu.ps , could anyone help us resolve this issue.

Best Regards.