It makes it worse if you allow them near ducks. My ducks actually pulled in a layer and drowned it in the pool... and continued to play with it and try to eat it.I'll quote a friend of mine who raises 300 chickens a year and refuses to feed cracked corn, only whole corn. " If a chick is too stupid to choke on a piece of corn it was too stupid to live". Yes he said that when he had a FB chicken page.
I would be more concerned why a 3 week old chick is that frail. I have hd a few broody's by choice and sometimes not release their young at 3.5 weeks old and the chicks did just fine on their own and thrived.
Out of hundred upon hundreds of chicks I have had 2 or 3 drown.
I've only lost two to drowning. Both caused by the ducks.