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Their food should only have at most 35% protein, too much protein can cause health problems especially to hogs that aren't very active, their fat should be 15% or less too unless they struggle with keeping weight on due to being very active.
Maybe check out the sticki under nutrition called beginners guide to hedgehog nutrition to improve the biscuit you feed.
As long as your changing the food gradually and not suddenly it shouldnt cause any problems, but even so changing it too much can cause problems, can't you maybe buy a bit more of the food she's on now to prevent needed to changing it so often ??
Most hedgehogs do go through quilling again around 10 months, just watch for bald spots. Not sure about the hair loss though.