I really don't think it's a calcium thing. Maybe since they are just getting started they are unpredictable
Below is the info for the pelleted feed they are getting. In addition, we are adding cracked corn, red wheat, greens, and oyster shell. I had also read on here somewhere that too much corn makes chickens stop laying? Maybe it works the same with ducks. We're too new at it to know.
Buckeye 18% Layer-Breeder (10550)
TYPE OF FEED: complete
FORM OF FEED: pellets
PACKAGING: 4 ton bulk minimum/50 lb paper bags
SPECIES: poultry
AGES: laying hens and breeders
FEATURES:
Pelleted for improved performance and intake
Reduces wastage and improves cleanliness
Additional Vitamin E added to improve egg hatchability in breeding birds
Contains high quality porcine meat and bone meal as a natural source of calcium and phosphorus
Contains corn gluten meal as a source of betacarotene, a natural pigmentation for improved egg yolk color
Contains added fat as an energy source
GUARANTEED ANALYSIS:
Crude Protein, Minimum 18.00%
Lysine, Minimum 0.89%
Methionine, Minimum 0.37%
Crude Fat, Minimum 3.50%
Crude Fiber, Maximum 4.50%
Calcium (Ca), Minimum 3.00%
Calcium (Ca), Maximum 4.00%
Phosphorus (P), Minimum 0.55%
Salt (NaCl), Minimum 0.10%
Salt (NaCl), Maximum 0.60%
INGREDIENTS: Ground Corn, Soybean Meal, Porcine Meat and Bone Meal, Wheat Middlings, Corn Gluten Meal, Alfalfa Meal, Animal Fat (preserved with BHA), DL-Methionine, Calcium Carbonate, Salt, Calcium Phosphate, Manganous Oxide Ferrous Sulfate, Copper Sulfate, Zinc Oxide, Ethylenediamine Dihydriodide, Sodium Selenite, Vitamin A Supplement, Vitamin D3 Supplement, Vitamin E Supplement, Menadione Dimethylpyrimidinol Bisulfite (source of Vitamin K Activity), Riboflavin Supplement, d-Calcium Pantothenate, Niacin Supplement, Vitamin B-12 Supplement, Choline Chloride, Folic Acid, Pyridoxine Hydrochloride, Thiamine Mononitrate, d-Biotin.
FEEDING DIRECTIONS: Feed as the sole diet to laying hens and breeders for maximum production and for improved hatchability. Hens may also be fed 5 pounds of Buckeye Layer-Breeder Pellets per 100 birds daily along with their regular ration to encourage additional daily feed intake for increased production. Maintain a clean,fresh supply of water and oyster shells available to the birds at all times. For top production, maintain light on the birds between 14 and 16 hours per day. Do not feed Buckeye Layer Breeder Pellets to poultry which are not in production because of the high calcium levels in the diet. This is particularly true of young growing birds.