Peas have niacin in them but do you know how much you’d need to feed for them to get adequate Amount they should have daily? Because you may have Pekins I’d start them out right away with Nutritional yeast sprinkled over their feed. It’s fine for the chicks to have it also NY has more niacin than brewers yeast. Even the grocery stores carry Braggs NY in spice section I believe or ask. Pekins are such fast growing breed they can develop leg issues over night it seems so why take a chance when you can supplement and keep it from happening?
@oldhenlikesdogs is right ducklings raised by mama duck usually don’t have problems because she shows them what to eat. Those of us who brood ours have to use whatever means we have available to help ours be strong and healthy. Go to Metzers web site and look up about why my ducks legs are bowed. If mine I’d want to keep that from happening.