Hi mk. I think I scored on this one. This looks to be the problem; Chrome is looking at your interface and trying to zoom on your text and content. I found a setting for accessibility which has a checkbox: "Force zoom override - override a website's request to zoom in."
I checked that box, and set my text size to 75% and reloaded your website. The result of which is that the interface has returned to the correct size. I'm not sure whether this is your website failing to respond correctly to an accessible content request or whether this is chrome failing to render the site correctly.