Header size/height different on other pages

Hi all. Total numpty at WordPress, but I’m having difficulty with the theme displaying a different header size (height) on the front page, versus all other pages. Is there additional CSS I can add that would ensure it’s the full size on the other pages too? I’ve tried a few options from other threads I’ve found in support for themes, but none of them seem to make any difference to the pages.

example:

.masthead {
height:360px;
}

The page I need help with: [log in to see the link]