For me, when a baby is not old enough to sit on its own, I really find the horizon lines like in number one to be unnecessary and distracting and very Walmart. I would find another way to pose them to avoid that. Use supersize bean bags covered with a blanket that becomes your full background, do more tummy shots. Do what you can to avoid separating your photo into two large colors as here, white and aqua blue.
Like shot number two. You used the entire white background and that was great! I would guess her to be about 5 months? They are almost sitting up, but not quite and they STRUGGLE to try when you sit them down. They LOVE their toes and when they grab them, as in shot #2, it allows you more room than when they are stretched out full. One trick to try with babies that you want to hold their toes is 1. Just have mom or dad grab their fingers, lead them to grab the toes and hold them while you wrangle a smile out of them. Instruct parent to pull away instantly as soon as baby smiles or you say "let go" and snap real quick. 2. Put a tiny piece of rolled up transparent tape under their toes or behind their ear. they will almost always reach down to grab their toes, or reach up with a hand behind their ear which is adorable, and you snap.
Another thing with shot #2, watch the details. Enlist parents to help make sure that shoulder straps are tucked down. Overall shoulder straps are the bane of a baby photographer's existence. They ALWAYS bunch up and you must always tuck them down again. Again, as for details, that green diaper is distracting and could have been white tell parents in advance, simple enough, or keep a small dark and a white diaper cover on hand. Once they are sitting up solid, this doesn't matter as much because they are angled forward more and you won't have that issue.
Also ask parents to help you with the drool thing. Sometimes a droplet hanging off the lip can be adorable, most times it catches the light and is a distraction. I always ask parents to help and tell them that while most will wipe the big drool, it is the "wet" that they leave behind that causes the problems with reflections and please help to keep the mouth area dry. It is easier to wipe it than fix it in post processing.
Love, love, love the light in this baby's eyes! Really beautiful catch lights and the light you used really shows the perfection and softness of her skin. Overall, great job and she is a real cutie patootie. Would love to see more. Think I'll follow your link to the rest! Sue Cassidy