Based on the photograph, these black spots are more suggestive of early childhood caries (ECC) rather than simple stains. However, a clinical examination is required to confirm whether they are superficial stains, enamel defects, or active cavities.
Formula milk and frequent night-time feeds, especially if the teeth are not cleaned afterward, can increase the risk of early childhood caries. The supplements you mentioned are not usually the primary cause, although some syrups can contribute if they contain
sugar.
Next Steps
I recommend scheduling an in-person visit to a pediatric dentist at the earliest. Early treatment can prevent progression and help preserve the primary teeth. In the meantime, gently clean your child’s teeth twice daily with a soft brush and a smear (rice grain-sized amount) of fluoridated toothpaste, avoid putting the baby to sleep with a milk bottle, and limit frequent sugary snacks or drinks.