need help swith my chicken

We have 2 buff orv and 1 RID the RID was born on 4/1/14 the buffs are around the same age give or take a few weeks. We found about 3 weeks ago 1 egg in the coop without a shell and one in the yard no shell then we opened the area for laying in the coop a few days later there was another egg no shell, in the laying area and what looked like another no shell under the roosting area, it was mixed in with the pine shaving so it wasn’t anything to really look at. Anyway nothing since then. Then about 3 days ago my husband closed the coop door by mistake when I went to lock them up for the night the 2 buff were there but the RIR wasn’t. long story short the RIR was outside the coop the next morning my husband was out at day break looking for her. When I got home from work that day I was looking for her the buff were around the RIR” Martha” wasn’t my husband went to the area were she came from in the morning and we found her sitting on 15 eggs and 3 more were around her. Now she hasn’t layed in about 4 days now. So many different answers for this ? do we lock her in a run ? do we lock all in the run and then move them to the coop in the evening ? I would love some feed back on this problem. I have read that the no shell thing is ok being they are young and this happens. I read to put fake eggs in the laying area that worked for 1 bird that 1 time. They get all the stuff they need food wise. Is Martha being broody now since we took her off the eggs ,because she hasn’t layed that I know of. I want to keep them locked up so we know what is going on. My husband lets them roam the yard (1.1/4 acre) If they are laying out there we will never know. I looked up what time they lay and that is all times I seem to be reading. Thank you who ever can help with this problem