I have checked the issue.
All the img tags of your post have a class named ‘alignleft‘ and a width property is set with importance like ‘width: auto !important‘. It is overriding the width-height(150*150) style.

To fix it, you can try the below CSS in the ‘Appearance → Customize → Additional CSS‘ field.

CSS:

.entry-content .entry-image-link img {
	width: 150px !important;
	height: 150px !important;
}

Hope the answer helps.
Thank you.