Product image problem – Woocommerce with Creativo theme

I’m using Creativo theme with woocommerce for a client project. In this theme, the woocommerce plugin is pulling a smaller-scale version of the main product picture (198×300) to show on a product page with a larger image area (more like 300×450). As the smaller image gets ‘upscaled’ in the display, it distorts and ‘fuzzes’. That is unacceptable to the client.

Is there ay way to modify the plugin code to force the plugin to use the largest version of the image as the product image, and so fix the blurred focus?

Temp example location http://kattywom.www82.a2hosting.com/admin/shop/books-and-chapbooks/animal-soul-by-mary-carroll-hackett/

https://wordpress.org/plugins/woocommerce/