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There is a reule below that adds a top margin to images that are inside a paragraph
.wp-caption,p img{margin-top:0.4em}
Depending how you are inserting the image you may be able to avoid the image to be placed inside a paragraph tag. or else, you can override it by adding the rule below to the theme Global Custom CSS Rule box
p img{margin-top:0;}
Now if you need to keep that top margin for other images inside paragraphs, you may need to add another selector to restrict the rules to the pages or area in question, or you will need to add a class to the images so you can make the rule target only these
for example
<img class="nomargin" src="..."/>
Then
p img.nomargin {margin-top:0;}