Blue Iris

Hi all - I'm a new Blue Iris user. I've added my cameras and can view them all. However, some of them have an odd green border around them and are sized slightly differently. I have seven cameras in total. Three have this border, four do not. I've compared all the camera settings as best I can and the settings appear to be identical between them. All the camera models are identical. Clearly there's something I'm missing. Any help would be appreciated. Thanks in advance!