My son drank Enfamil A+ before 12 months,and drank Nestle's ready for drink formula after 12mths when we went out.He drank homo milk at home. Nestle's powder 有点上火 when my son drank.
When we were in China,and I bought a can of formula powder there,because I thought the milk is not enough nutrition for my son,but my son refused to drink formula,so I only trusted 香满楼牛奶 than other brands,and he drank Danone yogurt,too.Also,I added more solid food for my son,such as Chinese soup,meet,fish...
Your son is beter than my son,at least he wanted to drink formula.