Gallery Thumbnail resizing: variation in pixel dimensions

I’m adding a new page to my site with a gallery. I’m using Gallery Plus and Lightbox 2. Previously I’ve let the plugin autocrop images but for this page I’m cropping some specifically and letting some crop by default. When the thumbnails appear on the page their pixel dimensions change depending on what I did or did not do to them. The defaults are 100×150, but ones that I have cropped myself appear with varying sizes, I would like them to all be the same size.

All images are the same height but vary in width.

I have used these plugins to create a portfolio on another page, if it has something to do with using different plugins instead of the ones I mentioned that would be fine, just means remaking the portfolio.

Thanks for your time.