Mobile view side width issues

Site URL: https://round-algae-fj2m.squarespace.com/

Hi, i'm looking for some help with my site when viewed on mobile. On all of the pages, minus the about page, the screen can be moved from side to side, as if the site width is different for these pages. I don't remember changing anything, however, I do have some code in place to adjust image sizes, and header format. Not sure if this could be affecting it. Is anyone able to advise?

Site URL is: https://round-algae-fj2m.squarespace.com/

Many thanks,

Nicola

Try adding to Design > Custom CSS

html, body {overflow-x: hidden;}