Elsewhere in this discussion there's a Reddit posting by a pediatrician https://www.reddit.com/r/medicine/comments/uvcijm/a_pediatri.... Under four months, home made formula:

"Often has a dangerously different osmolality. Infants eat whatever they are given and have dumb kidneys, so are prone to hyponatremia or hypernatremia and every pediatrician has seen a baby die this way. Don’t do it."

See that and other discussions here about the differences between infant (above) and toddler formula.