3 canaries hatched during the last 2 days, what can I do to help to babies grow healthy?

the 2 mothers and the father are in the same cage with the babies, and so is the other female. Is that safe?

Feed the adults the absolute best foods possible, since that is what they are regurgitating for the chicks. You might visit a health store and buy powdered wheat grass to sprinkle on their food. It is loaded with vitamins, and excellent for birds. Some bird specialty stores carry powdered cuttlebone, which you could also sprinkle on the food for extra calcium for the adult females as well as the chicks. A breeder recommended Petamine, an egg food, for my brooding birds.The link below is from a canary breeder. I tried to copy/paste some of it for you, but she must have made a read-only web site, as it won't highlight. However, visit the link, she has instructions for making sprouts and other recommendations for nesting foods.As for the full house, I have never heard of a cage with two mothers sharing a father bird and an extra female in the nest. Remove the extra female. If you don't have an extra cage, perhaps a bird rescuer in your area has an extra to loan you, and humane societies end up with donated cages all the time when someone loses or doesn't want a pet anymore.Because one father is feeding two broods, constantly check that there is extra food so there is no territorial squabbling or malnourished or starving chicks.

good idea.