It’s not dusty you just didnt know that he pooped and so it dried up. Regularly check okay mummy. And also try to give more water to him. When they eat solids they need to drink water more too. Also what helps is the cerelac you can mix it with his milk instead of water so it will taste better and has also better benefits. Jiayou! You can do this mummy!
change to vegetable or fruit purée instead and see if it’s the same.