If you cut back on the treats, their layer feed has calcium which they can utilize, that will help tremendously.
For the 2 that are having laying problems, give them both 1/2 calcium tablet like Caltrate for 4-5 days. No more than that since excess calcium can do damage too.
Getting your feed situation straightened out, hopefully you won't have many more problems. I like to give mine goodies too, but that can pack on the pounds too - fat hens can build up stores around the organs which can make it hard for them to lay eggs or the excess fat can cause Fatty Liver disease.
A few other things that cause egg laying problems are stress/overcrowding, being picked on and history of respiratory illnesses like Infectious Bronchitis and Mycoplasma.