Removing white space between images

I’m using Ghost primarily to send out a weekly newsletter. I’m having trouble uploading 3 consecutive images that I want to appear connected because Ghost automatically inserts a margin on top of each image. I was able to remove the white space by inserting this html:

.kg-gallery-card, .kg-image-card { --gap: 0; }

but the white space is still present when the post is sent out as an email. Any idea how to get rid of the white space in the email?

Any help would be appreciated! Thanks