5 of your locations were 100% spot on for me. However, I didn't have the 6th baby in "Asteria." I found them in "Grandery" on the path where there is a bridge and a lower path to enter the forest. Take the lower you'll hear the child crying. Break a rock you go inside a small cave with the child. You went to far by one screen, if you end up in the section with the water falls.

I was about 86% game completion when I got this quest. I was about 90% game completion when I started. So maybe some locations are different depending on what you have and haven't uncovered? Still this guide was really useful. I was starting a run headed to "Asteria" when I heard the final baby crying.

I have different locations than you, it seems the safest bet is to look for the hidden chest on every map.

Thanks for this guide, but I can confirm I found one outside of the ones you ID'ed. I had some of the same ones, yes (e.g., the one in Asterios, Yeldrim, and the two in Grandery), but I also just found a third one in Grandery. I think some might be locked to specific spots, but others randomly go to a secret?

Could you clarify the location?
The Stonedale one is before the captain, and they don't need to be discovered in any specific order.

I didn't collect the third in Jaroba, I did it in the last "stage" before confront the captain, in Grandery.
I think I know why: when you rescue all, there are 8 babies in the hub, not 6. Is it possible that you need collect only 6 but there are 8 locations?

Thanks for sharing! It's cute and saddening at the same time