Ok... I believe I was wrong before. I NOW have all 4 Barred Rocks laying. I received a tiny beige egg today and since ALL my eggs were laid in the nest boxes, I was able to watch the trail cam footage and confirm.
Also, I received my fake eggs today to replace the golf balls as 
@TwoCrows suggested and when I went to put them in the nest boxes, I discovered the Blue Australorp laid in the nest box! Finally, she figured it out! The fake eggs still came in handy, though, because they've been fighting over 1 box and they started spreading out to the other boxes.
I received 7 eggs today! All 7 of my layers gave me an egg. Still waiting on 4 more pullets to lay their first.