Thank you for your query. It is most likely that the black flakes you are seeing in your baby's stool is a result of the iron supplementation in her cereal. This is a common side effect of taking iron and is nothing to worry about. Some children develop constipation
with iron supplementation, but as long as she is opening her bowels regularly and comfortably I would not worry.
Very dark tar like stools can be the result of blood loss somewhere in the digestive tract. This is very uncommon in babies. So if you notice your child has episodes of severe distress, is pale, lethargic or not growing as expected I would suggest that she is reviewed by a pediatrician
I also wish to add that her treatment with oral thrush
seems particularly prolonged. It is worth getting her seen by a pediatrician to confirm that she does indeed still have thrush and not persistent milk residue (which is really common). If so, I would suggest changing her medication to a miconazole
gel. There are also other things you can do to prevent the thrush from recurring. You can sterilize all bottles and cutlery she uses. If she uses a pacifier, change it to a new fresh one. Since you are breastfeeding
it is worth you taking some treatment for thrush as well.
I wish you all the best and hope you find this information useful.