In Ethos stack, the masonry layout is designed to display the featured images along with each post titles. At the moment, all of you post does not have any featured images in it. Please edit it so that the featured images will display inside the grid boxes.
I noticed that your posts displays Video in it. Why don't you use the Post Formats so that the video will display in the masonry grid. To know more about post formats, please check this out: https://codex.wordpress.org/Post_Formats, https://theme.co/apex/forum/t/meta-options-posts/143
And if you want to display the post excerpts, it would require you to install a child theme. What you are trying to accomplish requires a template customization, we would highly to suggest that you use a child theme. This allows you to make code changes that won’t be overwritten when an X update is released. After your child theme is setup, please review how we recommend making template changes in Customization Best Practices.
Hope this helps.