She is our new arrival, the cage is a glass aquarium turned on it's side so that the opening faces front. The front is a custom cut piece of plexiglass with vent holes routed through and a locking system to hold it securely in place. I use flexwatt tape on the underside attached to a light dimmer for temp control.
I keep the "hot" side at a substrate temp of 90-95 degrees F. The "cold" side runs about 70-74 night/day. Ambient temp 1 inch off the substrate is a bit lower but she has a good thermal gradient on the substrate. This may be part of the problem, I never really know if the care sheets I read are referring to substrate or ambient air temp measured 1" off the floor. I use an IR contactless temp gun to test the substrate temps.
Humidity was initially too high for the first week I had her (around 92%). I needed to adjust the ventilation to bring it into the 60% range. With the problems I have noticed, I decided to replace her corner water bowl with a much smaller one to drop the humidity to around 50% while I figured out what was going on with the rattle. She has been eating well, though I did not feed her last night because she may need to go to the vet and I didn't want to invite regurge.
I am measuring the humidity in the cage with a analogue dial RH gauge from Flukers and a digital RH LCD unit for general home use. They seem to agree within a few percentage points.
I am really trying to get everything right, from what I have read online and discussed with others, but I have only been keeping snakes for about a year and a half now, and have never kept a BC. So, I would love to hear from those of you with ActualExperience(TM) LOL!
Also, this isn't a "how can I get out of a trip to the vet" post. I have no problem at all making an appointment and shelling out the cash if it would be better for the snake. I tend to be overly paranoid about the health of my reptiles, so this could be no big deal at all for all I know. But having never kept a BCI before, I have a little new parent hypochondria.
Thanks everyone.