I am also new to the forum, I have had my zebra finch for about 7 weeks. About 3 weeks after getting our cute little couple, they blessed us with 5 babies. I wasn't totally prepared for them to mate so fast, but we are figuring it out together

The babies are 4 weeks old, when do their beaks start change colors and I can distinguish male from female?
Thank you for y'alls help