It’s because of the plugin that you’re using. It’s adding code for the .wrap which affects the entire site. I’m not sure why it has !important when that would affect everything (it’s not good practice). I would recommend removing that code, or overwrite the code by adding your own in your theme’s style.css file for the .wrap.
Here is the code that your plugin is adding –
.wrap, #dashboard-widgets .meta-box-sortables, .ui-buttonset {margin:0 !important;}
If you still need to use this plugin and you’re unable to fix the css….then add !important to the .wrap in your style.css file around line 813
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