I've got my first batch of eggs in my incubator. Today is day 3. I candled them for the first time. All but one of them have a large dark mass. I guess that's the yolk. In 4 of those 6, it's moving around when I turn the egg. Is that normal? I have told myself that these eggs are just a learning experience and it's ok if they don't hatch. But you know that I would love to have at least one or two make it out.