Yes they have grit, changed regularly and kept dry. They have layers pellets. I put tonic in their water. They get scraps and greens and are allowed our for a couple of hours in the evening, all day when I'm at home. They look ok. They have been wormed.
"The first pullet egg may be soft-shelled until her system gets into its stride. If it continues, make sure that the birds are getting a balanced diet such as that provided by a commercial free-range or organic layers ration. Such feeds will usually contain calcium and phosphorus in the right ratio (around 3.5-4% calcium to 0.3% phosphorus). Providing a little crushed oyster-shell or calcified seaweed will ensure that any deficiency is rectified, for the birds will not take more than they require.
A shock can also make a hen lay a soft-shelled egg. My own observations are that if a flock is caught in a sudden shower of rain (for they are sometimes too dim to run for shelter), a few soft-shelled eggs are often produced the next day, but by the following day, theyre back to normal.
It is when soft-shelled eggs or misshapen ones are produced regularly that there need be a cause for concern. Veterinary advice should be sought. Conditions that adversely affect eggs include Newcastle disease (a notifiable disease to the authorities) and Infectious bronchitis, but there would be disease symptoms showing in the birds themselves if either of these was present. Hybrids are normally vaccinated against them.
Egg drop syndrome (EDS) is also a viral infection that results in a reduced number of eggs, as well as an increased number of pale-shelled eggs. Birds do recover from it but egg production may not get back to its previous level and there may still be a proportion of deformed ones produced. It can be vaccinated against."
Are they just coming back into lay? It's been a late start to the season. Hens can lay a few softies whilst things get back into the swing of things. Is the grit an oysters she'll grit or other calcium supplement?
Have you used flubenvet to worm? Are they getting enough natural daylight?
Maybe they are hybrids getting older, but my four year old hybrid is going strong.