If your humidity is too HIGH you don't want to add more humidity with a humidifier. And if the other bator is running at a good humidity you don't want to take humidity out of the air. Chances are that incubator has an incorrect hygrometer. Your best bet would be to go ahead and fill it with water and use it as a hatcher only until you can check the hygrometer against a hygrometer you know is accurate. Leave all eggs that are on days 1-17 in the bator with the seemingly more accurate hygrometer, and put the hatchers in the bator with the wonky one. As long as the temp is accurate and steady where you need it, filling the wells and maybe adding a sponge should give you enough humidity for hatching. If you are lucky enough to have any hatch, you can judge by how well they hatch as to wether adding another sponge would be beneficial.