Howdy again Fred!
This get a bit more complicated. With just CSS you can override the stretching, but then the image will get cropped instead. See:
#tribe-events-content.tribe-events-single .cmsmasters_single_event_inner .cmsmasters_single_event_img .tribe-events-event-image img{
width:auto;
height:auto;
}
In order to do more than this you will need to modify your theme’s templates. Your theme is explicitly setup to make all event featured images a certain size. Any image that’s not the size will either need to be stretched or cropped. If you are pretty versed in CSS and have a little bit of theming knowhow you can adjust this using a theme override (Themer’s Guide ) Your theme already has these overrides in place so all you will need to is modify them. However since I am not familiar with your theme I can not be more specific than that here.
Hopefully that helps get you pointed in the right direction here, and help you choose which of the available options if any you’re interested in. Please let me know if you have any questions. Cheers!
– Brook