Hay, constipation sa 8 months is pretty common, lalo na kung nagsisimula pa lang siya sa solids, a few of us noticed the same thing sa aming babies! When it comes sa Cerelac, usually one scoop per two tablespoons of water is the standard mix, pero since bawat baby may different needs, it's really best to check the package instructions or ask your pedia kasi ma-adjust mo depending sa consistency na gusto mo para sa kanya. Try din to add more water-based foods like fruits, veggies, or puwede ring coconut water to help with the constipation, pero if it persists, definitely bring it up sa doc para sure na okay lang.