Adjust tabs block styles

Hi there

I struggle using the tabs block.

My goal is to have the active tab with a border bottom line only. The other tabs should not have any border. Using this code:

.uagb-tab {
	border-bottom:none;
}

.uagb-tabs__active a {
	font-weight:bold;
	border-bottom:2px solid black;
}

It seems that using “uagb-tab” only has no effect, the border is still displayed.
Do you have any ideas why this is not working?

Thanks a lot
Michael