Changing Of FORMULA MILK

Hi po s mga parent. Kwento ko lng po. Si baby ko po since mag stop n sya s BM from her mom, SIMILAC na po ang gamit nyang milk hnggng s ngyn. She is already 1yr and 7mos. But lately napapancn nmen nagiging constipated sya. May nkpgsbi sken n ung milk nya ay mataas s iron content na nagkocause ng constipation. Mahina sya mag water at mapili tlga s pagkain kya less ang fiber nya. Kya we decided to change her milk to S26 Gold. Sa ngyn her stool nmn ay soft at mejo loose. Should we continue her new milk or ibalik nlng ulit s previous milk nya? Or part lng ito ng adjustment nya s bgong milk? Salamat po!