[Theme:Tesseract] layout issue on mobile

Probably an obvious one, but I am not a tech person at all, so be kind

we’re using tessaract 2 and are having an issue when displaying the site on an iPhone (all flavors) in portrait mode. Looks fine in landscape or on larger screen, so there is something not quite right in the way the width is set somewhere, but haven’t been able to sort it out. You’ll see that there is a “band” of white space on the right-hand side, as if the width of the page was constrained to something smaller/too small in that specific configuration.

here is the site: https://www.fitbux.com

TIA