In truth, 45% won't hurt it and, in this case, foliar spraying at lights out becomes an option so she doesn't dry out.
Ideally, the want it a little damper, but I doubt it will affect your final results in any noticeable way.
Take a bucket and fill it with water. Put an absorbent cloth over the edge, half in the water, half outside the bucket. Place a fan blowing on the rag. Assuming the rag wicks up moisture, this should raise your humidity enough. And don't worry, the low humidity will help you later on as they get bigger, your RH will go way up!