My LO couldn’t tolerate milk based, sensitive formula or soy. I believe 50% of infants that don’t tolerate the milk base also cannot tolerate the soy. It took a week or so to see how much he couldn’t tolerate it. Dr Phillips from MArci Kids also told me the hiccups are a result of too much gas in the stomach, so he may not be doing well with the soy. We put our Lo on the added rice starch, the protien is broken down a lot making it much easier to digest, it is like night and day…it is thicker and we have had no problems with it. His gas is normal and his stomach doesn’t have the loud gurgling it use to make with the soy. He was also constipated on the soy.
Good luck, there is so much trial and error when trying to figure out what is best, but when you find the majic como it is all worth it.