Hi grit and calcuim are two different things. They need the grit to digest their food and the calcuim is from the shell, unless of course you buying the mixed grit and calcium.
I wonder if they need a bit of protein if they are eating the eggs or a lack of water? Some of the reasons that hens eat their eggs:
The causes that incite hens to eat their eggs usually result because of poor husbandry or management practices. Chickens do not naturally eat their eggs. Once the management of the flock is restored to an acceptable state, the egg eating will stop. The list of major causes and corrections are listed below. A factsheet entitled Prevention of Egg Eating discusses the subject in more detail.
- If shells of the eggs are thin and weak, provide proper diets as discussed in the nutrition section to correct the problem.
- Not enough nest space is provided. Provide at least one standard nest for each four hens.
- Keep plenty of soft nesting material in the nest so eggs will have a cushion on which to lay.
- Collect the eggs more regularly, at least 2 or 3 times daily. The longer the eggs remain in the nest, the greater chance of breakage and consumption.
- Provide plenty of clean, fresh drinking water. Hens need greater amounts of water than other birds and may consume their eggs for the liquid content.
Chickens do need protein so are you making sure they are on a good balanced laying food? I give mine extra protein, they love mealworms lol, and will eat a bit of cat food too, although i have been told by some people they shouldnt have cat food others swear by it....but i only give it rarely...
Some chickens just have a break from laying. They dont generally lay everyday as they work on a 24 hour cycle. I get eggs from all my hens about twice a week, then other days, 3 eggs or 2....
If they are healthy looking and you are feeding them right, and giving them lots of fresh water, and perhaps some greens i wouldnt worry about them too much. MInd you i am not an expert and I am sure one will be along to tell you other reasons for it.