another soft shell query

One of my ex-bat girls has been laying soft shelled eggs for the last week whereas all the others were laying perfectly normal ones. Then today PomPom, my skyline, laid 2 soft shells by 8am, despite being the last one to lay yesterday, at around midday. I only have one skyline so knew the eggs were hers.

All my girls have access to small oyster shell as I found they hardly touch the larger stuff, but I have read that they can sometimes have difficulty absorbing calcium because of a lack of vit D. Even though mine are free ranging, what are people's thoughts on the use of cod liver oil or AD&E powder? 

An egg shell requires 3 grammes of Calcium which is equivalent to about 7.5 gramms of oyster shell or limestone.

That's quite a lot in a day and at 4% in layers feed it's very nearly 200 g of feed per day.

Treats will cut down on their calcium intake.  Exbatts will already be short of calcium.

A drop or two of Cod liver oil each week after a long dim winter is a very good idea and will help them to absorb calcium.

Is that drop or two per bird or mixed in with the pellets, Aunt Sally?

Depends how many hens you have CM.  If very few just a drop on a small square of bread (home made wholemeal fo course).  If you have loads of hens a small amount on their pellets will be fine.

Only got 8 now, AS - nearly said 9, still not used to Aggie being gone 

Thanks for the advice, both, will give it a shot.