site changes when I'm logged out

Not sure what’s going on.

Logged in, it works fine. 3 columns.
When I’m logged out, it switches to a 1 column layout, stacking all my divs on top of each other.

I’ve checked my CSS and don’t see anything that could cause this.
Any suggestions or ideas?

Website here
if you want to log in to troubleshoot the differences I’ve set up a generic user:
usernames: guest
pass: guest

Thank you for any advice you can give me!