Thank you so much for using our theme and thanks for your questions too. If you need to add the overlay on the inner pages top image, it needs a customization of theme. So, we recommend you to make the overlay on that header image through photoshop and add that image in place of header image. Go to Appearance > Customize > Header Options > Header Image. Hope, this will help you to make as your need.
If you have any confusion, let us know.