Eat fruits like dragon fruit, kiwi and etc. My10mo rarely has hard stool. We feed her fruits two meals a day. Can try to introduce leafy greens too. And my baby is also taking biogaia in the morning .
Swap cerelac for food high in fibre. I swapped it for Gerber Oats and introduced fruits/veggies as well. My lo got constipated from cerelac too.
try prune puree