I don't know how often you are giving her solid food, but the brochure we got from the pediatrician recommends 2-3 meals a day at nine months. At nine months they are pretty capable of eating, it's not practice anymore (that was 4-6 months). Yes, it's messy (I strip Bug naked to feed her) but it sounds like your breast milk might be making the decision for you, it's possible that it's either not as nutrient-rich as it used to be or that miss Mouse just needs more (fats, iron) than she is getting. Like you I don't think that a "fourth percentile" number is necessarily bad but I would be worried if she had dropped, implying that something had changed. If she is not getting all the nutrients she needs now she may have a hard time being physically healthy in later years, that's what would worry me.