Wa'alaikumassalam sis! Sabar je, constipation dengan formula changes memang common, especially kalau tummy sensitive, a few of us tried Similac Step 1 juga and some babies just tak cocok even if the first box was okay. Hopefully dapat buyer cepat for your unopened packets! Mana tahu ada mum friend dalam group yang kena same issue or baru nak try Similac. Goodluck with the sale!