I usually candle on day 10 (my hatches were Muscovy, which take 35 days) and I wouldn't be too worried unless I saw an obvious clear or blood ring. It's not an exact science, so even if I suspect a clear or just don't know what I'm seeing, I'll leave the egg in until the second candling - you can tell more accurately at that point.May I ask what kind of development you see at day 9 with your ducks? Like I said I have Blue Swedish set and feel like I'm not quite seeing development as I should on day 9! I candled just a bit ago and don't see movement. All I read is on chicken and what I should see with them.
At the first candling, I'm expecting to see some blood vessel development (veining) and would be pleased to see a black eye blob.