Hello!
I believe Woocommerce is changing your images sizes. Follow these steps to change single product image size:
Go to Appearance > Customize
Then go to WooCommerce > Product Images
Write your desired width in “Main image width” field.
Click on “Publish”.
I hope it helps.
Bruno
Check the image sizes defined in your theme for the products and make sure that you upload the images of same aspect ratio.
