Can I Change Just One Page On GridFocus Theme?

I use Grid Focus as my theme.

It has 3 columns.

I would like to add a Forum to my site, using Mingle Forum, which ends up functioning as a page taking up one of the columns.

But because there are 2 other columns, and Forums tend to need more space, it ends up being crowded.

So my question is, can I modify just the page using Mingle Forum, so the other 2 columns are deleted on just that page, and the Mingle Forum page takes up the whole width of the site?

My site can be seen at https://bit.ly/tqns3Z

Thank you!