Hai! Possible la tu sebab perubahan susu, a few of us mums noticed our toddlers punya tummy yang agak sensitive bila tukar formula, so it takes a few days for their digestive system to adjust. Tapiii kalau najis dia consistently berubah atau ada tanda-tanda lain macam demam, kembung, or muntah-muntah, better la check dengan pediatrician just to be safe, sebab kat age 1 tahun 3 bulan tu kena monitor closely. Normally dalam 3-5 hari dah settle, tapi jangan risau untuk call doctor kalau worried!