Submenu turned black

Site URL: https://www.groei-praktijk.nl/coach-op-jouw-school

I've been using the following custom code for months now:

/*kleur dropdown menu*/
.header-nav-folder-content {
    background: rgba(0,0,0,0.05) !important;
}

/* underline width */
.header-nav-folder-item a {
    display: inline-block !important;
}

/*underline currently active title*/
nav a::after {

  border-bottom: 0.5px solid #000000;

  content: '';

  display: block;

  position: relative;

  width: 0%;

}

nav a:hover::after,

nav .current-menu-item a::after {

  width: 100%;

}

However, suddenly the submenu below the title/tab that is active has turned black!

How do I fix this? Thanks a lot!

Lisette

First image attached: how I want it
Second image + third image: how it is

It looks like you solved with this code?

.header-nav-folder-content {
    background: rgba(0,0,0,.05) !important;
}

@tuanphan

thank you. Strangely enough it solved itself.. the dropdown was black as can be seen in the screenshots and without adjusting the code, a few days later it was normal again…