This is not directly related to the theme. This usually happens when the image uploaded is too small for the space it's being displayed in. HubSpot automatically resizes images, so you should always upload the largest size possible for the area you are using.
For example, if you are using a full-width image section, try uploading an image that is at least 1920px wide.
On the other hand, you can always access some specific sizing options (where available) in your modules, by navigating to Styles > Image from the left hand pane after selecting your module in the content editor.
Back to Knowledge Base
Comments