Sometimes they're a little slow on the uptake of the oyster shell. If I were you, I'd mix some layer feed with the start&grow. If you mix it 50:50, the resulting calcium will be 2.5% rather than the 1% or 4% or the other two feeds alone. This may help them till they get regulated and it won't be too much for the younger birds - more like a pre-lay diet.
Sounds like your Amberlink has completely wiped out her bodily stores of calcium.
During the 18 hours a hen builds an egg shell she uses up a significant portion of the calcium in her body.
That's the problem with having birds of various ages approaching POL over a span of time.
Commercial egg farms have birds of identical ages housed together and provide a pre-lay diet of about 2.5% Ca for up to 4 weeks prior to laying to beef up the skeletal storage.
Egg shells require about 1.7 grams of calcium to form. Along with other metabolic processes of the laying hen, 2.5-3 grams of calcium total may be required daily.
High producing hens like yours create enormous Ca demands. 3 grams is more than what a hen can absorb from the diet for a hen that lays every day. To build an egg shell the hen must utilize the calcium stored in medullary bones. That calcium gets replaced every day in the diet.
Brittle bones or osteoporosis is possible if sufficient calcium isn't already stored and adequately supplied in the diet.
Grains are less than 1% calcium so no scratch grains should be given especially to new layers.
http://www.nutrecocanada.com/docs/s...-formation-and-eggshell-quality-in-layers.pdf
http://www.gov.mb.ca/agriculture/li...eggs-and-your-small-flock-of-laying-hens.html
http://naturalchickenkeeping.blogspot.com/2013/02/calcium-mixed-flocks-vs-mixed-feeds.html
It may even be necessary to separate the birds for a while till you get the layers calcium stores restored.
