Change the Appearance of the Featured Image on Home Page in Oxygen Theme

Hi everyone, my name is Angelica and I need some help please ??

I’m using the Oxygen theme and have noticed on my home page, that the images for my blog posts don’t all show up as the same length. I don’t set a featured image when I publish my posts so I don’t know if this pertains to slider image or featured image or something else? All my images are custom size to 2000×2000 in my blog posts. Majority show up as the correct length they should so not sure why others are different.

My website is – https://brooklynchicktravels.com/

Can someone please help me out, thank you so much!