I have 3 girls - all 21 weeks. A Rhode Island, an Easter Egger, and a Barred Rock. Lately the Rhode Island has been squatting down submissively when I pet her. We got our first egg today! But I'm not positive who laid it. I know it wouldn't be the EE. The Barred Rock is by far the largest, and has grown the fastest... But the RIR is the only one who has been submissive. Is there a way to look at the chicken or the vent to be sure?