Dolfi remember what I said, Humidity is NOT a number. and if I ran 30-35 I would have big wet chicks. why? because of the high humidity here even with the coal stove going right now...
If your not weighing, you need to watch air cells, and ONLY USE HUMIDITY AS A TOOL, NEVER a number.
What I do is only add a tad, LIKE A SMALL 1"x 1" dish of water, ONLY IF the humidity gauge reads below 18% during the first week and then pencil air cells and compare to the drawings at day 7,10,14 and 18. I am always picking up eggs and candling to check the air cells and more than those times listed. I have a good feel for them at this point, you will get there too the more you incubate. If the air cell looks good, I change nothing (I leave the dish) if it looks too small I remove that little container, most times I have NO WATER in the bator until at least day 14.. It all depends on your area and humidity levels.