Hi Steve, and welcome to the Forum.
Sorry to hear about the problems with your hen. It would help to have a it more information about her. How old is she? Do you know what breed she is, and is she a hybrid who has been laying most days since she first started? Is she eating, drinking and pooing OK? Have you just started giving grit to the chickens, or have they had it before, or have they got access to grit anyway because you let them out into the garden sometimes? Has she ever moulted, or do you think she might be starting to moult?
If she's an egglaying hybrid breed, and is around 2-3 years old, it's possible she's coming towards the end of the store of egg cells all hens are born with. When they're gone, they're gone, and the bird hits the 'henopause' just as humans do. Hybrids bred to lay very large numbers of eggs in the first 2-3 seasons obviously use up their eggs sooner than purebreds, which usually lay less frequently, live life more in the slow lane, and consequently go on for longer. The first signs that a hen may be slowing down is often that she lays soft shelled eggs, lays less often than usual, or has difficulty in laying at all because the soft eggs are harder to push out of her oviduct. Extra calcium on the form of oystershell or dietary supplements may possibly help, but a good layers feed should contain enough for them - the problem seems to be that absorbing calcium is a complex process, dependent on interaction with other minerals in the diet, and this seems to get harder for them as they get older. Also of course, at this time of year, hens do slow down as the days get shorter, and I expect all your birds may be laying less often in response to less daylight, and maybe moulting also - hens can't find the energy and protein to grow feathers and lay eggs at the same time.
So there are several possible reasons to consider. If you could tell us more about her, we might be able to be more help.
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