Did I read correct, that you are treating 5 chickens to a quart of scratch/cracked corn each day?
If so, not only will they need a source of calcium sooner or later but you are running a serious risk of health issues (unless a quart is much smaller than it is her in the UK.) Hens will eat scratch in preference to their layer feed so that scratch will be reducing the amount of layer feed they eat and therefore diluting the calcium they ingest. Scratch is also higher in carbs and lower in protein that layer feed and your birds are at risk of becoming nutritionally unbalanced and over time potentially obese as a result. This can lead to the risk of several very seriious ailments including egg binding, prolapse, internal laying and possibly even sudden death due to Fatty Liver Haemorrhagic Syndrome. This occurs over a period of months rather than days or weeks but by the time you discover a problem it is often too late.
You would be well advised to dramatically reduce or stop the scratch and/or cracked corn before damage is done.
A reasonable quantity of scratch would be a tablespoon per bird per day and ideally not every day. Better to provide them with a healthier treat.
Birds including chicks will need grit if they have access to anything which is lumpy or fibrous, like vegetation..... basically anything that would require "chewing" if they had teeth.... bearing in mind that pellets and crumbles go to mush when soaked in water in their crop, so don't need any grinding/"chewing". It is better to supply it and it not be needed as not supply it and it them have digestive problems.