2 week old constipation

Perla
My 2 week old has been constipated for the past week and I dont know what else to do. I feed her Gentleease Formula (the purple one) and her poop has been coming out yellowish hard balls. The pedi told me to give her 1 ounce of water twice every day but it doesn't help. Please any suggestion on what I can do. Change formula? Any remedies?