^Humidity fluctuates, it can swing up or down often wildly depending on the conditions outside. If it is rainy outside, humidity goes up. I also live on the East Coast, where the weather changes without a moments notice. These people just don't get it, they are too worried about what their books, grow mags and the guy at the hydro shop says, and it is no offense to them they can't help it.
Think about it though, do you think the weather concedes to Cannabis? Nope. It would not have survived if it didn't survive/thrive in the face of some minor environmental stress like the humidity being not quite perfect. Not to mention that these plants are able to regulate the flow of moisture throughout the plant by opening and closing the pores on their leaves (stoma). As they transpire they take up water from the media, which is no problem indoors when you can just give your plants water. I realize some growers may be afraid of water.
The point is, I can assure you and the OP that any RH between 20 and 70 is fine for vegetating your drug plants indoors. If it is drier you're going to be watering more frequently. You could counter this with a more absorbent growing media.
Your primary concerns should be the temperature, your growing media and providing adequate lighting and a clean environment. 70 isn't really too cold to grow in, but that is a bit too cold for germinating seeds. Germination will be slow if anything at cool temperatures, use a seedling heat mat.