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You have not mentioned about her birth weight. That will give us an idea about how much weight she has gained.
Our criteria for good health in young children are their feeding, sleep, and activities. If all these parameters are normal, there is nothing to worry. She will eventually gain weight. You have also not mentioned what does your pediatrician says about it. Regarding white spots, I cannot comment, as I have not seen them, but children do develop many spots or rashes, but nothing to worry.
I hope you are satisfied with my answers. All the best.