Was she born in 2020? Or did one of them turn 17?
The Stimulus Checks are really based on your 2020 return we are filing in 2021. So any amount you already got will be reconciled on your 2020 return line 30. If you didn't get a Stimulus Check (and qualify) or you qualify for more it will be added to your 2020 return. But the good news is if they paid you too much they won't take it back.
