White Theme featured image not showing

Website is https://www.storyofthestudy.com

The images for my 2 recent blog posts at the bottom of the page are not the images I used for my featured image when I edited my post – in fact, they’re not my images at all. I suspect they’re default images that the theme provides. It’s been so frustrating trying to correct this and have my intended images show up for my blog posts – I hope there’s a simple solution I’m missing.

Thank you!