Completely clear eggs is one thing to look for. Give you idea if eggs were not fertile or if something went wrong in first few days. Those eggs you can mark and check again on day 10 and if no change/still clear toss them.
The other thing is how your air cell is growing. Unless you weight eggs and monitor percent loss the air cell growth is the best way to monitor water loss. If it's way off from the model you adjust your humidity. Lower if cell is tiny and more humidity if cell is too large.