I am sorry about your lost babies. I know that ducks' nutrition is extremely important. Feeding layer pellets at that young age is not a good thing. It is not enough protein for them and too much calcium.
Here is the information that I base this comment on. They are much like chicks...they go through food stages and as chicks their bodies cannot handle layer feed.
What to feed your pet duck
This is our recommendation for a domestic duck diet, based on input from Avian Veterinarians, Wildlife Rehabbers and Ducksperts all over the globe. We list food choices that are readily available to consumers.
Avoid commercial diets designed to grow ducks fast for meat or commercial egg production. These diets often contain medications that prevent communicable diseases in large duck communities, and may be harmful to your duck. NOTE: Most newer formulations have improved - still best to be cautious.
Ducks do well on non-medicated pelleted mash as a staple, supplemented with fresh vegetable trimmings, chopped hard-boiled eggs, tomatoes, cracked corn (keep out of ponds if you have fish), garden snails (NOT if you use snail bait or pesticides), worms, night crawlers, bloodworms... They enjoy floating coy food occasionally. Most items are available at pet and grocery stores.
Protein levels are very important to your duck's stage of growth.
Ducklings need starter feed with 20-22% protein for 3 weeks.
Adolescents do best on 16% protein.
Adult ducks need 16-18% when they are laying and 14-16% if they aren't laying.
Too much protein can cause a condition called "Angel Wing" where the feathers on the wings protrude upwards. Too little can cause nutritional deficiencies and serious health problems including death.
Generally a mixed diet of commercial pelleted food such as Layena supplimented with green forage (or lettuce or other greens if forage is not available) and scratch grains or cracked corn will provide for a healthy flock.
Here are some duck diseases/disorders that you might want to look at it...
Duck Virus hepatitis
Duck virus hepatitis is a highly fatal contagious disease of young ducklings, 1-28 days of age. Ducklings are most susceptible at the younger ages and gradually become more resistant as they grow older. The disease is rarely seen in ducklings over 4 weeks of age. The onset of the disease is very rapid, it spreads quickly through the flock and may cause up to 90% mortality. Sick ducklings develop spasmodic contractions of their legs and die within an hour in a typical "arched-backward" position. The liver is enlarged and shows hemorrhagic spots. To prevent this disease, keep age groups isolated and vaccinate breeder ducks with an attenuated live virus duck hepatitis vaccine (to produce maternally immune ducklings).
Toxins
Ducks are particularly susceptible to certain toxins, and in some cases strikingly more than chickens or turkeys. Therefore, duck caretakers must be especially diligent in preventing ducks from consuming or being exposed to these toxins.
Aflatoxin poisoning
Molds (fungi) that grow on cereal grains and oilseeds before and after harvest produce a number of toxins that are particularly harmful to ducks. By far the most toxic of these substance is a group of toxins called aflatoxins. Aflatoxins are produced by the molds Aspergillus flavus and Aspergillus parasiticus. Ducks are highly susceptible to these toxins. Very small amounts will cause high mortality. Wet harvest conditions encourage the growth of this mold.
Botulism
Ducks that have access to stagnant ponds or other areas where decaying organic matter (animal carcasses, in particular) is found may consume toxins produced by the bacterium Clostridium botulinum. This happens when temperature and other conditions are right for the growth of this anaerobic spore-forming bacterium. Botulism causes a progressive flaccid (limp) paralysis of the neck (limberneck), legs and wings. Affected ducks usually die in a coma within 24-48 hours.
Castor bean poisoning
Incidents of high death losses in wild ducks, due to consuming castor beans (Ricinus communis) have been reported in Texas. Castor beans contain ricin, a toxalbumin known to cause toxicity in humans and domestic animals.
Rapeseed meal
Some older varieties of rapeseed meal contain erucic acid and goitrogens at levels high enough to be harmful to poultry. Ducks are much more sensitive to erucic acid than are chickens and turkeys. Genetically improved varieties of rapeseed (Canola) contain much lower levels of these toxins. However even Canola meals should first be tested in ducks before their use in duck feeds on a large scale.
Insecticides, rodenticides
Duck keepers should take care not to use insect sprays or rodent poisons, that are known to be harmful to ducks, in areas accessible to ducks. Some insect sprays are highly toxic to ducks, such as parathion and diazinon. Always read the directions on the insecticide container carefully before using around ducks. Rat poisons that contain Warfarin, an anticoagulant, if consumed by ducks, can cause them to bleed to death.
Good luck with your duckies.
