I am using the following in my .htaccess which redirects the page to the secure port

Options +FollowSymLinks
RewriteEngine on
RewriteCond %{SERVER_PORT} !^443$
RewriteRule ^form\.php$ https://domain.com/form.php [R=301,L]
However, since all the links on my site are relative path, when you leave form.php and continue to navigate the site, you remain on the secure https://

How do I only have the form.php on the secure port?