Responsive probleme on differents devices

Hi,

We have probleme with responsive design on this site : http://cimex.acces-provisoire.fr/

We use your theme "Be" and your "Decor" Demo (this one : http://themes.muffingroup.com/be/decor/)
Your demo is well, and images are responsive with differents devices : but images on our site aren't ... They are zoomed and pixelised.

responsive.css is present on our FTP but i dont understand why in your demo website there are no problem ..

any ideas ?
Thanks in advance,

Kind regards,

Charline Hattier