ya, if you could post pics, it could help quite a bit. idk about that kind of thing developing over time, but anything could happen...
my guess is its genetic because they all have the same condition. its verry unlikely that they would all get the same toe hurt in the same way at the same time...
bent toes can be a result of a fluctuation in tempature during incubation. could also just be the result of inbreeding somewhere down the line. did you hatch them ur self, or get the chicks from a breeder?