decrease grid space

Add this to your custom styles:

.threecol .entry-container {
	padding: 4.3%;
}

You can play around with the 4.3 value until you obtain a desired result.

You may also want to add this:

.threecol .entry-title {
margin-bottom: 0;
}

i’m not seeing the code on your website.

I’m sorry, I misunderstood. This is the code you need to play with:

.threefourthcol .threecol .entry {
	margin: 7.5%;
}