Customise wordpress site

Hi,
Please are you able to customise the header images on my website such that they will fit into the header space. As you can see on the links below that the images are currently stretched. I have tried other options on the theme settings such as contain and auto fit but they do not give me the result I wanted.

http://www.wtarmy.org/meet-the-captain/
http://www.wtarmy.org/blog/

I look forward to your response.

Thanks