Custom Code to target higher-res images stored on SS CDN?

Site URL: https://ruthannez.com/

I have a custom code implemented on my site to use a gallery as the banner on my home page. This morning, images were displaying nice and crisp- and after adjusting the code in my FTP software for the h3 tag, all of the sudden the images (as confirmed by the url upon inspection) are displaying at 1024px! Does anyone have any idea on how to "force" SS to use higher-res links/images? I'm baffled, as again, it was just fine this AM and I legit did not touch anything else!

Edited to add: I'm pretty sufficient in using code and figuring this out. I have developer mode enabled, I just don't know where to go looking or what code to use to target the use of a higher-res image link.