73º on the cool side is too cool with ambients this low it is possible the snake simply will not eat as it is questionable if it can get core temps warm enough to digest its food. Humidity isn't a huge problem until it hits 30% so at 40% I'd not be concerned. Your cool /ambient temps NEED to be addressed typically most suggest 77º as the low end and some 75º but 73º is definitely very cool.

Many thermometers have a potential error the average is +/-2ºF I would always assume that if it is possible it is actually out this could mean that 73º is actually 71º (also why I don't like seeing 75º because 75º could be 73º too cool)

You need to address the cool end temps! Most like to use 80º as a correct cool end. Little snakes often do better with cooler temps but not too cool!!