Welcome to BYC!
There very well could be a bully in the flock, I know I have some in mine. Most of my hens have sores on their combs because of a rooster, but it sounds like you don't have one. Try spreading out some feed and sitting and watching. Dominant hens will be the ones who choose the best perches at night, claim the best food and water, and don't let others get near a feeding or drinking spot they claim. The dominant hen also likely won't have missing feathers or sores on her comb.
In my experience, because their combs are so large, leghorns are more prone to comb damage, so they could just be getting them cut on sharp branches or wire.
I hope this helps.