Hide hover underline on vertical secondary navigation only

Site URL: https://evolutionofbrilliance.squarespace.com/

Hello, I have created a vertical secondary navigation. I have also added some code which creates an underline on hover on both primary and secondary navigation. My issue is, I only want the underline to appear on the primary navigation, and not the secondary vertical navigation. I need some help with the code please as I can't figure it out!

Password is: 123456

Many thanks!!!

Edit your code to this

@media all and (min-width: 700px) {
    nav.Header-nav--primary a {
        display:inline-block;
        float: none;
    }

    nav.Header-nav--primary a:hover:after {
        transform: scalex(1);
    }

    nav.Header-nav--primary a:after {
        display: block;
        content: '';
        border-bottom: solid 2px #fd8f32;
        padding: .2em;
        transform: scalex(0);
        transition: transform 250ms ease-in-out;
        z-index: 999;
    }
}

You're amazing Tuan! Thanks again!!!!!!