I'm no expert, but since my VFT's (dente, red drag, green drag) are all growing so well, especially the dente, I think it's ok for me to speak up.
First of all, I agree with statik - boiling water makes things worse, unless you're collecting the steam, condensing it, and using that. Might as well just go to the market and get a gallon of distilled water for under a buck - a gallon lasts nearly a month for the 11 CP's I grow.
This might stir up some controversy, but I find that feeding (insects) helps whenever my VFT's look shriveled. I noticed that when a VFT is unhealthy, I need to feed a smaller insect than usual in order for the trap to be able to handle it. Baby spiders always work very well for me, so do small silverfish (although silverfish tend to be difficult to remove afterwards). In about three days after feeding, shriveled teeth on traps spring back straight and coloration becomes healthier. I have personally never had an overfeeding problem. When in doubt, I feed, and my VFTs seem to appreciate it.
I have personally never tried reducing light and water on an unhealthy VFT. That may or may not be good. I always give it full Southern California windowsill sun (direct for about 5 hours a day, indirect for an additional 8 hours). Humidity does not seem to be a necessity. My windowsill humidity is always below 50.
Leo