I have a 9 month old who is on one bottle a day before his nap, then he nurses morning and night. But I've only had one family who kept the naptime bottle past about 14 months of age. The child in your care isn't getting all the nutrients from fruits and veggies that they need to grow. I know all parents have different ideas about how to feed their children, but maybe you could research and find some articles that you could email to this family? You know your clients best. A face to face talk is usually the best method when the issue is this big.