Help baby no longer likes formula?

My 9 month old twins have been eating solid foods since about 5 months. Recently they have been introduced baby juice. Now they almost refuse to drink their bottles. They will drink a few sips, then just play with the bottle and if they actually finish the bottle, they are not full. Is their anything I can do to insure that they are getting their nutrients? I do mix some in their oatmeal but I don