Don't panic! It's probably fine.
Nature is tough! And even under a hen things happen and fluctuate with weather, etc.
But getting a hygrometer is a great suggestion. I got one from PetSmart in the reptile area that is digital, and battery operated, and was only about $10. I also stuck a "weather station" type from Lowes in the 'bator. It tells temp and humidity remotely (it also appears to be the most inaccurate. Ironically branded, Acu-rite.) It was about $20, and I can see it from the display that can go with me within the house. And lastly my incubator has a readout on top, so I triangulate the three, with my knowledge from trying to calibrate them. Not sure I trust any of the three, but I know I'm in the ballpark.
Lastly, while I'm far from an expert, I would suggest not "over-compensating" for what you think was a lack of humidity for a brief period. There are some great threads and articles about weighing eggs and tracking that to manage humidity. And obviously candling for a look at the aircells. You'll be fine!