Add to your page setup:
tt_content.fdfx_3cols_pi1 {
10.stdWrap.dataWrap=<p class="csc-fdfx_3cols_pi1-header csc-fdfx_3cols_pi1-header-{field:layout}">|</p>
15.dataWrap = <p class="csc-fdfx_3cols_pi1-subheader csc-fdfx_3cols_pi1-subheader-{field:layout}">|</p>
}
to change the rendering of header (10) and subheader (15). Header and subheader will only be rendered if they are available.