Variation Images

One problem I can’t seem to fix is how the images are stretching for the variations. When a customer selects a variation the image attached to the variation does not look nice at all. The original images were 300×500 pixels and I spent 7 hours today resizing them to the default thumbprint size of 150×150 pixels and uploaded 2 of them. Do you know what the default size is for variable images that are attached to the variables?
If you take a look at https://www.piperspixels.com/product/tartan-custom-note-card/ and select the variable “Dunbar” (my original 300×500 size) or “Black Border and lettering-No tartan” or “No Border” (uploaded today as 150×150 size) you will see what I’m talking about. They look horrible on my screen. They are pixelated and blurry.These are the images that are attached in the variation settings to each variation of the product. All my other images seem okay, but just the variable choice image attached to each variation.
Please help.
Thanks