I am highly concerned about your complaints regarding you granddaughter. Her weight is good. There is no compulsion for giving formula feeds to babies. You can very well continue with the breast feeding and semi solid complementary foods. Regarding smooth patch on tongue, it is better to get this examined by your pediatrician
and let him decide further management. As there are several conditions with normal coating over tongue and also some conditions like oral thrush
, vitamin B complex deficiency which may require some treatment. Do not worry, your child will be getting well very soon. Thank you.