Perhaps you need to use another formula. It may not be agreeing with their bodies. The "green" poop is often because of the iron content in formula. But this is a necessary vitamin at this age to prevent anemia and is in most formulas. Yes, I have tried Kirkland formula too... but my son did not have this problem with it. He likes it, and we had no unusual reactions to it, and my Doc said it was fine... the ingredients are almost identical to the more expensive "name" brands.
Keep in mind, that for babies, the consistency of "poop" is NOT like adults. For babies, it should be or is usually about the consistency of oatmeal or cream of wheat. Not runny though. Even in toddlers it's this way. This is what I was told by a Pediatric Gastroenterologist. If it's harder than that, or in firm balls...then that is constipation.
Ask your Pediatrician though.
Take care, and all the best to you as a SAHM... it is a precious time and experience. I too am a SAHM. Even though it means we don't have as much money... I wouldn't trade it for the world.
Good luck
~Susan
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