I currently have 2 domains that access to the same folder on my server: metrikstudios.com and ziced.com.
I want the users that enter through http://
You could simply add another RewriteCond to check if the host is metrikstudios.com
RewriteCond %{HTTP_HOST} ^metrikstudios\.com [NC]
and it should look like this:
RewriteEngine On
RewriteCond %{HTTP_HOST} ^metrikstudios\.com [NC]
RewriteCond %{HTTPS} off
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI}