How long has she had those rashes for? Are the rashes accompanied by a fever and other discomforts? Did she eat or come into encounter with something that she wasn't supposed to? Keep monitoring her rash, if it goes away in a few days, could very well be heat rash. My friend's baby had a bad case of it recently due to the scorching weather.
I would first take her to her pedia so they can have a look and assertion the situation. They might help you go through your baby's routine and even what you eat. Just incase it is an allergy rash. Then if further investigation is required, they will point you in the direction of the best skin specialist.
Does it look imflammed? If yes then it's eczema. Recommend go Naaman skin clinic at Novena. Alot of mummy recommended it.. you can Google's their reviews. My LO went when she was 5 weeks old. By 10 days, ecezema all cleared.