I was suggesting that you change your light to come on in the morning so your girls aren't caught in the dark if they are down eating or something when the light suddenly switches off and they can't see to make their way back onto the roost at night. That COULD be a stressor!
My chickens ignore cats as they walk right past each other. Cats while an issue for chicks are not much of a threat to a full grown chicken. But even in cities there can be lots of other predators like raccoon, stray dogs... for us, even mountain lion (even in LA which is not where I am).
