i have 4 kittens that are just a couple days past 3 weeks old. 3 girls, 1 boy. the girls all weigh 15-16 ounces each, but the boy is the runt & he weighs between 5-6 oz. before this more accurate weight was done, the vet's office said as long as he's eating, not to worry, but i can't help it. i'm feeding a supplement of kitten formula because sometimes i see him get pushed out of the way of feeding by his larger sisters. does anyone know how fast does the mom's milk reproduces? then i can let him feed when his sisters are not, in addition to the supplement.