How can I remove spacing between images in my gallery block?

Please could someone help me here i've done everything i could and nothing has worked so far. I can't inject css since it's a premium feature. I would like there to be no space between the images. thank you xo

http://arnikaholland.com

Try this in Custom CSS:

#collection-65bcfdd51d16a53096ea0932 {
  .sqs-block {
    padding-top: 0px;
    padding-bottom: 0px;
  }
}

sooooo grateful !!! thank you it worked x