apache2 redirect not adding trailing / - apache

Question

Okay so I am having a little difficulty with my site, I created a sub-domain and it points to the correct folder /var/www/html/pathfinder/ but it does not create the trailing slash www.example.com
that causes an issue because then it attempts to load css files at www.example.comcss/file.css
I am using SSL and can't figure out what I have done wrong.
<IfModule mod_ssl.c>
<VirtualHost *:443>
DocumentRoot /var/www/html/pathfinder
ServerName www.subdomain.example.com
ServerAlias subdomain.example.com
<Directory /var/www/html/pathfinder/>
Options Indexes FollowSymLinks
AllowOverride All
</Directory>
ErrorLog ${APACHE_LOG_DIR}/error_1.log
CustomLog ${APACHE_LOG_DIR}/access_1.log combined
SSLCertificateFile /etc/letsencrypt/live/www.subdomain.example.com/fullchain.pem
SSLCertificateKeyFile /etc/letsencrypt/live/www.subdomain.example.com/privkey.pem
Include /etc/letsencrypt/options-ssl-apache.conf
</VirtualHost>
# vim: syntax=apache ts=4 sw=4 sts=4 sr noet
</IfModule>
# HTTPS over SSL version
# Information: https://github.com/exodus4d/pathfinder/wiki/Apache
# Enable rewrite engine and route requests to framework ===========================================
RewriteEngine On
# HTTP to HTTPS ===================================================================================
RewriteCond %{HTTPS} off
RewriteCond %{HTTP_HOST} !^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$
RewriteCond %{HTTP_HOST} !=localhost
# First rewrite to HTTPS:
# Don't put www. here. If it is already there it will be included, if not
# the subsequent rule will catch it.
RewriteRule .* https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
# Rewrite NONE www. to force www. =================================================================
RewriteCond %{HTTP_HOST} !^www\.
# skip "localhost" (dev environment)...
RewriteCond %{HTTP_HOST} !=localhost
# skip IP calls (dev environment)
RewriteCond %{HTTP_HOST} !^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$
# rewrite everything else to "https://" and "www."
RewriteRule .* https://www.%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
# Some servers require you to specify the `RewriteBase` directive
# In such cases, it should be the path (relative to the document root)
# containing this .htaccess file:
# RewriteBase /app/
# Protect system files ============================================================================
RewriteCond %{ENV:REDIRECT_STATUS} ^$
RewriteRule ^(lib|tmp)\/|\.(ini|php)$ - [R=404]
# Rewrite "everything" to index.php (dispatcher) ==================================================
RewriteCond %{REQUEST_FILENAME} !-l
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule .* index.php [L,QSA]
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization},L]
# PHP global Vars (can be set in php.ini as well,...) =============================================
php_value max_input_vars 5000
php_value suhosin.get.max_vars 5000
php_value suhosin.post.max_vars 5000
php_value suhosin.request.max_vars 5000
# Activate PHP error log ==========================================================================
php_flag log_errors on
# php_value error_log "/www/htdocs/www.pathfinder-w.space/logs/php_errors.log"
# Cache Header ====================================================================================
# You should not change anything in here!
# New versioned files come with a unique path (e.g. ../js/v1.0.0/..) to force client cache busting.
<ifmodule mod_expires.c>
# fonts
<Filesmatch "\.(eot|woff2|woff|ttf|ttf|svg)$">
ExpiresActive on
ExpiresDefault "access plus 1 month"
Header append Cache-Control "public"
</Filesmatch>
# images/vector graphics
<Filesmatch "\.(jpg|jpeg|png|gif|swf|ico|svg)$">
ExpiresActive on
ExpiresDefault "access plus 1 year"
Header append Cache-Control "public"
FileETag None
Header unset ETag
</Filesmatch>
# css
<Filesmatch "\.(css)$">
ExpiresActive on
ExpiresDefault "access plus 1 month"
</Filesmatch>
## js/source maps
<Filesmatch "\.(js|map)$">
ExpiresActive on
ExpiresDefault "access plus 1 year"
Header append Cache-Control "public"
FileETag None
Header unset ETag
</Filesmatch>
# html templates
<Filesmatch "\.(htm|html)$">
ExpiresActive on
ExpiresDefault "access plus 1 week"
</Filesmatch>
</ifmodule>