Good afternoon! We are in need of assistance since we are very new to raising backyard chickens. We got our chicks in October, started out with 10 but 1 died a month later. The rest seem to be doing well and we are looking forward to eggs this spring but 4 of our chickens are displaying this white crust (see picture attached) near their ears and we have NO idea what it is. Is this an ear infection or some other disease? We've isolated them from the rest but don't know what to do next. Should we take them to a vet? Please tell us if you know what this is and what you think we should do. Much appreciated, thank you!