How to Remove Blurred edges or curtain effect on iMovie picture

I created an iMovie and saved the project. Some weeks later, I tried to add more pictures to the movie, but the new pictures have blurred edges like a portrait effect. How can I remove these blurred edges and have the picture a full landscape? I've checked settings on the original pictures and they are the same and yet somehow they're changed when added to the project.

Thanks in advance

[Edited by Moderator]