Sub-menu line height

Hi, I'm having an issue with the line height on the site I'm working on. I've set it in the Customize section and it looks fine, but upon saving there's too much space. I tried adding this CSS:

.main-navigation .main-nav ul ul li a {
line-height: 15px;
padding: 8px 10px 5px 25px;
font-size: 14px;
}

Which again looks fine until I click Publish and the spacing reverts back to the unwanted space. I've tried deactivating plugins and still get the same issue.