slider image height problem

I use the flexslider that came with the Respo theme by Themnific, one of the things I want to change is the slider not showing the full image – it shows the full width, but not the full height of the slideshow images. I looked around on the internet but don’t see any obvious(for my skill level) ways to fix this.
Any help or suggestion will be appreciated, here’s a link to the slider: https://www.mcx.co.za