Well, I know some people who live in humid areas can sometimes have trouble getting their eggs to lose enough moisture and that can be with absolutely no water at all added to the bator! What has your humidity been the first 18 days? And yes, you're right, even with all the good advice in the world there's nothing like experience for learning how to incubate correctly. So much of it is just trial and error and figuring out what works for YOU. Other people's advice won't always be suitable, especially where the subject of humidity is concerned!
It's a good idea to keep notes on each incubation. Nothing fancy, just something simple like checking and writing down the temp and humidity each day, and also number of turns if you're hand turning your eggs. How many eggs you started with, how many were fertile, how many go on to hatch. Then if you get a good hatch, you'll know to do the same thing again, and if you get a poor hatch, you can look back through your notes and try to figure out what might have been the problem.
Good luck!