Re: High light plants
If your light sits directly on the glass hood, I would elevate them a few inches; that will definitely help mitigate part of the problem. Sure, 32W doesnít sound like much, but when you consider LUX and PAR readings, even that low wattage can emit light too strong for plants over that small distance.
Based on the photo, it looks like some of those plants are getting burned. The bromeliad on the left looks like it has some burning. Elevating the light should help, but I would also cover the roots in damp moss to really help get them established and growing. You could probably keep that light st 100%, so long as itís elevated a few inches. I use a lux meter, and you would be surprised at how huge a difference just a few inches makes!
Simply put too, most of the plants in that vivarium will quickly outgrow it under optimal conditions. Your nepenthes will soon burn too, but not from lighting. Unless youíre washing the roots off, or using a form of filtered water, the roots will eventually burn due to mineral buildup from tap.
For ventilation, I think itís a necessity to have some form of ventilation ó even if itís minimal. However, as often as we go into our vivs to feed, maintain, etc., you have to consider if just opening the lid a couple times a day is enough. Maybe it is, maybe it isnít. Iím on the opposite end of the spectrum, in that I actually give my vivs a ďdry outĒ period of a few days, every couple weeks or so. I think itís important for the health of the entire little microcosm. When I say dry out, I just mean not misting for a few days, and maybe opening the top a little more frequently. Personally, iíve found that to benefit both the plants and animals best. Youíll notice ventilation varies from person to person, and itís often dictated by what is in the vivarium already.
Socratic is right in that you canít diagnose based on the browning tips alone, but I can tell you that the close light placement, in combination with ventilation, or lack thereof, helps narrow it down a bit. If you wish to keep it 100% sealed, you could always opt for plants that will tolerate the high humidity. I understand sometimes itís difficult to ventilate a viv properly!