One year old hen laying behaviour changed

I have a one yr old EE mix who has faithfully laid her eggs in the coop on a regular basis since February, I understand she is at an age that she "may" be molting but her behavior has me stumped as I have never come across this...

Over the last four days or so I have found a soft shelled egg under the roost, I didn't think much of it as I have several pullets that should start laying soon, the other day after feeding the flock for the morning I was standing out at the run and watched this year old hen squat and pop out an egg out in the dirt.. something she has never done, thought it was weird but didn't give it anymore thought... Last night I went out before dark to check all was well and happened to walk in the coop just as this same hen popped out a soft shelled egg while sitting on the roost...
My flock is on all Purpose feed as I have Turkeys and younger chickens who should not be on layer feed, I give Oyster shells on the side for the layers and have never had an issue with the established layers..

Thoughts?? As I have said I have never experienced this and wondered if its just a stage of molting I have just never encountered.

 

oh ok... Maybe that was or is the issue, I had been letting them get down to the "powder", putting out the shells once every few days.. I will put it out daily..
My flock is pretty spoiled, not only do they get fruits and veggie from us but from all our neighbors too, we have asked them to not throw bread out but for maybe once a week and let us know before they do (to much not good) but they get all kinds of fruits and vegies and proteins every few days.
Thank you for the link and hopefully it helps others experiencing this... weird that it is only one hen this is effecting that I can tell.

 

Thanks! I just went out to fed and water the flock for the day and she was back on the roost looking like she was going to lay an egg right there.. Watched her for a bit and then went to take care of the rabbits, when I came back she was down checking out a nest box so we shall see... I had just given them a scoop of oyster shells last night and it was gone, so I doubled the scoop for today.. or some dumb reason I was concerned they would take to much.. I know, doesn't matter how long a person has had chickens there is still so much to learn..