These 3 jumpers are in different wools because many knitters don’t like knitting larger jumpers in thin wools.
With this pattern you can knit the jumper for all your girls.
I used a 4 ply or fingering wool for the baby of 5 to 10 months old.
I used a 5 ply sport wool for the older baby of 8 to 15 months old.
I used an 8 ply DK wool for the toddler of 1 to 2 years old.
All with the same number of stitches.