70% humidity isn't bad if yout substrate isn't damp or anything. Its humidity that over the 85-90 range over a long period of time is when u start worrying. I guess with a higher humidity like that, you may want to clean and disinfect the cage more often to make sure bacteria isn't growing out of control, as well as keeping an eye on the substrate to make sure no mold is growing. Keeping all those things in check, 70% isn't much to fret about.