I have a form which partly pre-fills after filling in an address field. Is it convenient to give green check marks on the fields they didn't fill in themself?
Yes, if the pre-filled data is user-editable
If the user can still edit the pre-filled fields, they need to know that the current data is valid and also if any changes they make, are.
Make sure all pre-filled data is indeed valid. You don't want to pre-fill data that somehow fails your validation. Test this.
No, if the pre-filled data is not user-editable
If the user cannot change the pre-filled data, make it clear the fields are inactive and do not validate them.
The user doesn't need to know if they are valid because they didn't enter or alter any data. If the data is somehow invalid, the user can't do anything about it, so they shouldn't be bothered with a warning.
Although it may seem useful that inline validation for pre filled form fields is ok, it depends on the kind of field that you are addressing. If the address fields are not critical to further information from the user, then you can use the green validation. Else it might be better to let the user validate the information.