One of my BOs just started laying this week and of the four eggs she's laid (that we know of) 3 of them have been rubber eggs. The first had no shell at all and broke and the other two have had a very very thin shell. I'm almost positive that she laid at least one good egg -- we got five eggs from 5 layers the other day so one of them had to be hers. She's 22 weeks, has been on layer feed for 3 weeks, and we added oyster shells this week. I also started giving them yogurt. All of the others are laying perfect eggs. If this keeps happening, at what point do we consider it a "problem"?