Girls need advice. We fed one with formula from home. Recently, the ba…

Girls need advice. We fed one with formula from home. Recently, the baby started refusing food sometimes. We thought it was the formula, so we switched to another one. We transitioned smoothly, though not in two weeks, but in five days. With the new formula, the same story - he eats then refuses. From the new formula, diarrhea started. I read that the intestines adapt and maybe diarrhea is possible. It's been a week already, and still diarrhea. If he went 1-2 times at once, then today 4. So, question: can we switch immediately to the old formula? Or do we also need to transition gradually? On the old formula everything was good and with stool and tummy. How should