Hi A.,
My son is 11 months old now and I too noticed a slow down these past two months, however, this past week, he has been nursing more often but just for a few minutes here and there and when he wants to nap. He is eating solids and the only time he gets juice in a sippy is when he's having hard bowel movements, we give him some prune juice. We live in Tucson where it is very dry, so we ALWAYS keep a sippy cup filled with water around so he can drink from that whenever he is thirsty. What it really boils down to is this: your child's needs will fluctuate from time to time whether it's solid food, water or breast milk. I agree with others that there really isn't a need for formula at all when you can provide water, breast milk and solids. Just offer your daughter something of each whenever she seems like she needs it and let her decide. You can't go wrong. A hungry baby will eat and a thirst baby will drink and whether that is from you or a sippy cup, she is getting to be old enough to decide for herself. Babies don't need juice is what my pediatrician told us. It's bad for their teeth and has way too much sugar. If you're worried about iron and nutrients in your milk, just make sure you offer her a balanced selection of solid foods. For our son, it was hard to figure out how much to give him from a jar because sometimes he would eat less or more depending. Now he is big enough for finger food as he has 6 teeth and I give him a variety of those to feed himself with a sippy cup filled with water. Once he starts throwing stuff on the floor and playing with his food, it's time to get out of the highchair. He lets me know if he wants to nurse then or not or sometime later if he didn't get enough of the solid foods.
Just trust your instincts and you really can't go wrong.
I really hope this helps. You've already done an amazing job so far by going this long so keep up the good work and you guys will figure it out!
Lucian's Mommy