You should ditch the lamps, and go with an UTH(under tank heater) on one side of the enclosure set at the mid 80's down on the floor substrate where the snake actually is, and the cooler side being a normal comfortable room temp as the rest of the house(mid 70's or so). They are mainly nocturnal dweller's and do not need all that blazing light source. That will help keep the humidity from being too low immediately as all that lighting is drying the enclosure(and snake) even more. But you also have to figure depending on where you live that these winter months setting in will also make the ambient relative humidity in your house even dryer STILL.
Most colubrids do well when the relative humidity is above around 40 percent or better, much lower than that and they can begin to have shedding issues. I have noted this personally for many years.
Simply ditch all that lighting and go with UTH, and make sure the snake has a few hides in each area, and things should work fine.
You can also ezperiment with covering portions of the cage top to to retain more humidity, or simply ad a "humid hide" container with moistened sphagnum moss inside it.
Whatever you do though, you need to closely monitor and KNOW what the temps are on both sides down where the snake is with an accurate thermometer. Guessing at temps can lead to serious health issues, and even death if you don't pay close attention to what is going on as you change these conditions.
regards, ~Doug
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"a snake in the grass is a GOOD thing" 
my website -serpentinespecialties.webs.com