Stopped laying

In one of our coops we have a RIR and two Brahmas. They are all about 18 months old. All three were laying on a regular basis. In late May, the RIR started setting. A few days later the two Brahmas stopped laying. Several weeks after the RIR's eggs hatched she started laying again. Still nothing from the Brahmas.

Three weeks ago the RIR started setting again. About two days into it when she got off the nest to eat, one of the Brahmas got in to sit on the eggs. She wouldn't move and so the RIR got in the next box. When the Brahma finally got out of the nest my son put the eggs in the nest with the RIR, she took them and continued to sit on them. We put golf balls in the other boxes and the Brahma (that took over the RIR's eggs) parked herself in the nest and stayed there. I was also hoping it would encourage them to start laying again. About two days later, we gave her some eggs from another coop and she took them. We thought if she is serious, we didn't want her just sitting on golf balls and nothing to show for it after 21 days.

The RIR's eggs hatched two days ago. If the Brahma's eggs are going to hatch it should be in the next couple days. I am doubtful though, because I think there are times she has been off the nest for too long.

All this being said, is it normal for other hens to stop laying when another in the coop is setting? This did happen in one of our other coops recently, but both started laying again as usual. The Brahmas have not been laying for three months.