Slideshow images are mixed sizes...

Willson Cummer

A weird thing: on one of the slideshows on my website www.WillsonCummer.com -- the Lake Ontario gallery -- the images are coming up different sizes. Let the slideshow run and usually the 4th image will display larger than the first three. Other images are also displaying large. The source images are all the same size.
Any suggestions?
Thanks!
Willson