As much as the feed might look more nutritious, feed changing should be gradual i.e introducing small portions of the new feed mixed with large portion of the other untill such a time that the birds have gotten used to the new feed in a less tarbulent and stress full way. Moreover always avoid making any changes on feed, housing unit or adjustments to laying boxes mid laying. Those are unecessary disturbance to the birds which stresses them resulting into reduced production or complete stop in laying and they undergo a process otherwise known as force moltting. Kindly try correcting the stress by adding egg formula(poltricin egg or egocin egg) into their drinking water.