You might try marking them so you can tell them apart when they grow. Their plumage does change as they get older and juvenile plumage is not exactly like their adult plumage. It is easy to get them confused as they age.
For them to be black sex links, your Australorp would have to have a sex linked barred gene and that gene should be dominant so you would be able to see the barring on your hen, at least in the tail if not all over. If yours are purebreeds, then I am confident the chicks are not sex linked. If they are not purebreeds, it is possible there is a recessive gene in there somewhere that might make some of the chicks sex linked, maybe, but I really don't think all the chicks would be. I think the Australorp has a silver gene but the extended black overrides the silver.
For them to be black sex links, your Australorp would have to have a sex linked barred gene and that gene should be dominant so you would be able to see the barring on your hen, at least in the tail if not all over. If yours are purebreeds, then I am confident the chicks are not sex linked. If they are not purebreeds, it is possible there is a recessive gene in there somewhere that might make some of the chicks sex linked, maybe, but I really don't think all the chicks would be. I think the Australorp has a silver gene but the extended black overrides the silver.
