Hey, maybe you already heard about this, but a friend once told me that this phenomenon is called "blue hour" (like the dusk time period), and it's when little ones in roughly their first year are mentally working through everything they experienced in the day. It's a big process for the brain and it takes time to work through. What helped, according to the friend, is being patient and gentle with the baby when she enters this period and just sitting through it with the little one. When they don't feel alone, they (sometimes) don't cry as much.

Happy to hear about the smiles, I hope you'll get to see many more watching her grow up