The lightbox shortcode does not support the titles for images currently. This would require custom scripting in order to achieve this. Try adding the following code in the Theme Options > JS:
var title = $(this).attr('title');
$(this).append('<h3 class="lightbox-image-title">'+ title + '</h3>')
Then add the following code in the Theme Options > CSS:
The above script extracts the title from your image shortcode e.g title="Martini Stone" and append it to the lightbox item whereas
my-portfolio is the class assigned to your lightbox images.
Don't forget to clear all caches including your browser's cache after adding the code. Let us know how this goes!