Couple of things... do you have a lamp now or just uth? 75 is far too low for a hot side. RI can happen with the low temps/high humidity. You should really pick up a probe thermometer ($12 at Walmart for a acurite indoor/ outdoor therm) to see exactly what the temp of your uth is.
How thick is your aspen?
The snakes are not really display snakes and he would be much happier in a low traffic area.

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