Blog posts cut off on mobile device

I have the same problem with my site on mobile phones (at least iPhones). I am using twentyeleven. Everything looks fine on a computer and iPads. The site looks fine on the Home page. But, when you open up to a blog post, it looks fine for a second, and then suddenly it shrinks so that the right side is blank. Looks awful. I am not very experienced, so this could be a very simple issue.

Thanks,

http://www.wholefoodsexplorer.com