that you describing seems to be dietary only. She may be on Earth's best organic formula feed but still nothing replaces a breast feed. Children may respond differently to these feeds and differently at different times too. The composition of these feeds also vary with the age of the child. I suggest you get that sorted out with your pediatrician
. At 4 1//2 months you can consider giving him top feeds. If you give him top milk, make sure you sweeten the milk by adding sugars. Place your child in luke warm water. It helps healing any cracks he may have developed near his anus due to hardened stools.
Hope this helps. God bless you!!!