Feature image is showing up in blog posts as too large.

I have read the posts here and tried putting code in the custom code area under appearance. That didn’t work. I looked at the media settings and they are as required. The image uploaded is according to recommendations. So, why is the feature image showing up as a HUGE image at the top of the post? There are no problems with resolution, it is simply just BIG.
Could there be a plugin conflict? Do you have a fix for this? I’m stuck and my client is waiting on me to fix the images.
 
Thanks!