your rubber eggs are what's called shell less, if you know a teacher, school kids love those eggs. plus another name for you comets, sex-links. from what you said your doing good. Is this your first batch of chickens? if so, you might start a collection, I started out with six, now I've got more than 400
If you keep getting those rubber eggs try to find out who's laying them because your hens could start to eat eggs because of them.
