Question about dry incubation

[NC Chicken Lover]

I am trying the dry incubation method for the first time, using a hovabator genesis 1588, forced air. With no water added, the humidity is running about 25-30%. I am incubating seramas. I thought the humidity was a little too low, so I have been adding about a teaspoon of water. every 12 hours. The humidity goes to about 43%, and then quickly decreases to baseline in about 12 hours.

Here are my questions. What % of humidity is too low? Is the fluctuation of humidity harmful to the developing chicks? I am currently on day 4, so I want to stop anything I am doing wrong, Thanks for any advice!