Permission of 775 not enough

The “user” running your webserver (sometimes _www, sometimes www-data, sometimes “nobody”) lacks the permissions to edit these files. You can either change them to be owned by that user or change them to 777. To find out what your web server user is, assuming you’re running apache, run ps aux | grep httpd in the command line and in the leftmost column, see what user it’s showing!

Cheers~