When do banty polish start to lay??

[Shoonell]

We have 4 banty pullets. One is a plymouth rock and three are white crested black polish. They are all the same age, about 21 weeks old. The plymouth started laying the cutest little eggs about 2 weeks ago but our polish have not laid one. Did the plymouth just come into lay early or do they start earlier than polish?? We are looking forward to one of our polish laying especially because she is no bigger than a big Robin. We figure her eggs will be quite the conversation piece for our neighborhood kids. Thanks to anyone who has info!!