htaccess rewrite rule only partially works

I have a basic htaccess rewrite file, however I am unable to get one of the rules to work when it is similar to a previous rule.

My code is;

RewriteEngine on

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d

RewriteRule ^gallery$ gallery.php
RewriteRule ^about-us/page-1$ page-1.php
RewriteRule ^about-us/page-2$ page-2.php
RewriteRule ^about-us$ about-us.php

gallery, page-1 and about-us all work, however page-2 does not.

Is there a way to get this to work?

I have tried a different order and if about-us is put first, neither page-1 or page-2 work