The photos aren't quite clear enough to be able to tell. However there are still ways you can find out even without us visually confirming.
The easiest way to sex guinea pigs is to simply feel just above their genitals. Male guinea pigs have a bone in their penis, which you can feel just under the skin as a firm line, as female guinea pigs do not have a bone in this area they will just be soft with no firm line. With practice you can learn how to expose their penis by gently but firmly pressing at the top of the line of the penis bone and rolling your finger down.
You can also try comparing them to some sexing photos of other guinea pigs. I find it easiest to tell by gently parting the genitalia. I will attach some photos of my own showing both a boar and a sow with this method, the photos are of guinea pigs who were about 4 weeks old at the time.
This is a boar, between my two fingers where his fur begins just above the genitals is where you would be feeling for the penis.