Grid defaults to 2 columns wide for mobile, I need it set at 3.

Site URL: http://www.cassidyrouth.com

Hi! I've attached 2 photos, the first shows what I'd like the front page to look like across all platforms, and the 2nd is what it looks like on mobile as of now. I've tried a few bits of code, but nothing has changed/fixed the issue.

I'd like it to display 3 columns on mobile for this grid, can anyone help? 

Thank you!

Try this CSS, then save & reload your site

@media screen and (max-width:640px) {
div#block-yui_3_17_2_1_1606925700289_19345 .slide {
    width: 33.3333% !important;
}
}