Header Transparency Issues

Something happened this week. I used to have the transparent background for the header across my site. But suddenly on the two portfolio pages, there's a black bar behind the header even though i set the header to transparent. 

Anyone knows why? Do i need some special CSS code to make the header transparent?

Hi. Add to Design > Custom CSS

/* Fix header black bar */
body#collection-6035ce92ad9aa279501fdff1, body#collection-60557cf11f8001702f18bbbf { article section:first-child {
    padding-top: 0 !important;
}}