Also, after researching on this site and asking similar questions, anything more than about 1.5 weeks age difference may lead to some killing or serious injuries (I have 9 week and 1 week chick difference. Here's a thread that I'm going to using as my play guide, it might help in your situation too. https://www.backyardchickens.com/articles/my-coop-brooder-and-integration.74591/