By default, your photos get automatically centred within their grid cells when they appear inside gallery content blocks. If you've got portrait images featured, that'll probably end up cutting peoples' heads off, since they tend to lie in the top portion of the frame.
You can add this CSS to your theme to tune that behaviour on all your pages, or add it as a CSS block on a page to affect just that page. This option will shift upwards from centred by 25%:
Or you can go all the way and top-align portrait images instead:
Here's the before:
Here's the result from using the first option to shift the view upwards by 25%:
The second option shifts the view upwards as far as it will go:
To apply the fix to both landscape and portrait photos (instead of just portraits), use one of the codes below instead. The first does a 25% shift:
The second one top-aligns the images: