If he won't drink, give him papaya or other juicy fruit.
I think I had it backwards. He should have a white dollop on his little green turds. Keep offering water, but keep fruit like melon in his cage until his turds have the white topping.
From what I read, cockatiel poop is light green. It's a bit odd, though, why the poop doesn't show the dollop of white urates. It could be because the bird is drinking a lot of water and the urates are mostly mixed into the poop, turning white as they dry.
I think it's a water issue. The bird...