Discoloration of foot .help needed

[aseel lover]

All my flock is exposed to new castle but this hen healthy tommorow laid one egg now i see the discoloration of foot ..what disease is this is this new castle?

 

[Shezadandy]

All my flock is exposed to new castle but this hen healthy tommorow laid one egg now i see the discoloration of foot ..what disease is this is this new castle?

Here's one of mine.
It's not disease, just genetics.