Water is something to take seriously – clean water drastically reduces your birds ability to get sick. Make sure the water is high enough in the cage so that the birds do not poo in it. Change it every morning, and check it in the afternoon, or as necessary. Do not use bird vitamins in the water, as they escalate bacteria breeding ability. The water cup needs to be washed with detergent each time – I have 2 cups, so I always have a clean one to change over with.