Hipp organic worked best for us but the health visitor did advise to be careful as switching can cause just as much tummy upset depending on age of your little one. When it comes to switching we were advised to wean so if you do 4oz for a few days do 3oz of your normal 1oz of your new one then increase and reduce as the days go on so it’s a gradual change x
I just switched but my issue was she was allergic and is now on CMPA milk. I tried the Sma one and she was exactly the same but that’s because of her CMPA. Also if you give pre-made formula it’s meant to help them. Seen so many people say it helps they just give them babies a pre-made formula twice a week and keeps them regular.