In your Portfolio Editor, you can easily correct this issue by adjusting a small bit of code!
Once you are in your Portfolio Editor, select Code on the top left.
You will then need to select the dropdown menu under HTML, CSS, etc., and click Collection in order to view the code for images.
On approximately the 4th line of code, there will be a line that reads: photo.image.large. You can choose from "large", "xlarge" or "huge" in order to increase the display quality of your images! Keep in mind that the larger the image, the longer it will take to load on some devices.
Always remember to Save and Publish once you are happy with the changes made to your Portfolio!