What is wrong with my new rescued chickens?

Hello everyone, I recently rescued 3 chickens and the area around their eyes look very different to my very healthy, already existing flock. I was thinking hay they probably weren’t get fed good enough but my dad is scaring me and saying it’s a thing called “foul pox.” If anyone is experienced and knows what’s wrong with them, or if anything at all is wrong with them, please let me know. Mt main concern is the areas around their eyes. Thank you!