Two weeks can be completely normal with BF babies. Breastmilk is brilliant for helping prevent constipation but it's so digestible, there's often not much left! If she's only had a tiny amount of sweet potato on top, that might be the cause?
You don't say where you live but if you're in the UK see your health visitor if you're worried. Of course if she's unhappy or in pain, definitely see your Doc.