Hi,
If you edit your menu item via the Joomla menu manager and check under the Products options tab, you'll see the "height consistency" setting. I believe this setting is activated in that menu item on your website. When activated, the javascript will calculate the height of the biggest product box and adjust all the other boxes in order to match it.
So, an easy solution is to turn off that setting.
I tried to look at the reason why this height consistency mechanism was creating a lot of empty space on your page. I think it has something to do with your template. However, with the plugin jspeed which obfuscate and compress all the CSS and JS on your pages, it makes it really hard to look at the problem and I couldn't find the culprit.