I've started my 6mos old baby on solids. He will be 7 mos soon. I sometimes mix cereal into his baby food because otherwise he won't eat cereal. I've noticed solids cause him to be constipated. To loosen up his food I mix water. He also drinks juice with water but not even an Oz in one sitting. I'm very worried I'm causing water intoxication. What am I doing wrong?