Column spacing set to 0, but site is showing a gap down the centre column

Site URL: http://leard.co.uk/

I have a 7.0 squarespace site but I'm currently putting together a new 7.1 site using the Gates template. The default is to have 3 columns, but I want 4, but when I change it to 4, there's a thin line running down the centre (image attached), even though the spacing is set to 0. Anyone know why it's doing that?

1 hour ago, steveleard said:

Site URL: http://leard.co.uk/

I have a 7.0 squarespace site but I'm currently putting together a new 7.1 site using the Gates template. The default is to have 3 columns, but I want 4, but when I change it to 4, there's a thin line running down the centre (image attached), even though the spacing is set to 0. Anyone know why it's doing that?

 

Try adding to Home > Design > Custom Css

#grid .item {
  border:none;
}

My testing