How to make additional menus responsive

I am using a child theme based on the latest version of Attitude.

Needing more menus, I followed the WP codex to create some new ones. At first I had the problem described here:

wordpress.org/support/topic/how-to-remove-the-navigation-menu-item-from-custom-menu?replies=2

which as you can see I resolved in the CSS file, but now I find that my new menu (under header, above content) does not show nicely on mobile devices, with the horizontal lines that indicate the Navigation. How do I fix this?

Tks
SP