You definitely don't want it fluctuating that much. 40-45% works best for me. Start off there, and then weigh your eggs later on. That's how you'll know your humidity is good and they're achieving the correct weight loss. They should lose about 12% of their weight. What day are they on now? It's...
Growth is most obvious by day 7, so for beginners it's best to do it then. Don't toss any until day 14 though. And mark and eggs you're unsure about with a question mark to reassess later. Good luck!