A newborn rat pink is usually around 6g, which is the size of a small fuzzy. They grow quite rapidly and by day 2, can easily be 8g in size. By 3-4 days, they are the size of a large mouse fuzzy. But there is some thought that a mouse fuzzy is better than a newborn rat pink as there is more calification of the bones, so what you are already feeding sounds fine.
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