My guess: they are probably not getting enough food.I have 20 hens, 8 Buff Orpingtons, 5 Silver Laced Sussex, 2 Isa Browns, 4 Ameraucanas, and one mystery hen. They all are 9 months old. I have lights in the coop and a few months ago, one hen started laying. Then three days later we had a cold snap and she stopped laying. I have not got an egg from any of my hens since. I am feeding them Scratch and Peck layer feed which I ferment. I rotate through 3 containers and do a batch in each; they ferment 3 days before I feed them to the chickens. I thought they were not getting enough food (at the time I was feeding them 1/4 cup per bird a day) so, last month I upped their food a little. As they still didn't lay, I upped it even more a few days ago. Now I ferment 4 cups per batch which doubles to 8 cups (just under 1/2 cup per bird). Recently I started feeding half of it to them in the morning the rest in the evening. They always eat all available food at a feeding.
A common estimate is 1/4 pound of dry feed, per bird, per day for standard sized laying hens, in addition to as much water as they want to drink.
That would mean 20 hens eat a 40 pound bag of feed every 8 days. Or they eat a 50 pound bag every 10 days. What size bag do you usually buy, and how long does it last?
When people measure and weigh dry feed, they usually find that 1/4 pound of dry feed is between 1/2 cup and 1 cup, depending on the brand. That would mean 20 chickens need between 10 cups and 20 cups of dry feed per day, not the 4 cups of dry feed you are using. Your chickens are probably starving (literally), and that is why they are not laying.
Water is not a substitute for food. Measuring the amount of food after you add water, then comparing to someone else's dry measurement, is going to cause trouble (whether you are using cups or pounds, the problem is the same either way: water makes the food bigger and heavier, but does not add any more nutrition.)