Get rid of row gaps in portfolio grid on mobile view

Site URL: https://www.jaci-cruz.com/

Hello. I am trying to make my portfolio grid go to two columns on mobile view rather than stack. I've got the two columns but can't  get rid of the large gap in between rows. 

here's my code

/* 2 Column Portfolio Grid */
@media only screen and (max-width:640px) {
.portfolio-grid-overlay {
display: inline-flex;
flex-wrap: wrap;
justify-content: space-around;
}
.portfolio-grid-overlay .grid-item {
width: 40%;
}
}

That helped a little but it the gap is still large. When I inspect it it seems to be attached to the grid item 

Because you haven't removed this code yet. Display inline-flex & width 40% override Squarespace core code, caused problem

THANK YOU SO MUCH!