[THEME: Responsive by CyberChimps] image overlay in mobile view

Hello,

in the below screenshot you’ll see the smaller right image lined up nicely with the other image in desktop view:

but when i collapse the desktop screen, the smaller image overlay the larger one. I want it stacked below the larger image:

My site is build with Responsive theme by CyberChimps. Sorry I cannot give the URL because I develop it on local. Can anyone tell me what to do to fix the responsive problem?

Thank you!