You are correct in that they need more light and airflow. However, I think that the light problem far outscales the airflow problem. Removing the tops from the terrariums would probably allow for adequate air exchange, and humidity would still be maintained by moisture evaporating off of the soil surface/water trays. On the other hand, several plants show clear signs of light deprivation. Although the flytraps are growing, they are getting longer and more spindly as you observed. These are indicative of etiolation, which is a plant's growth response to inadequate light.
Can you provide the lumen (measures light intensity) and kelvin (measures color temperature/spectrum) ratings on your lights? Usually they'll have something like "2500 lumens 6500k" marked somewhere on them. This will help give a better idea of the light conditions that you have currently. Wild flytraps and sarracenia generally grow in full sun, with many tens of thousands of lumens per square meter. Many of the colors you see in healthy plants only develop in strong light as these pigments are used by the plant to protect itself in very bright light. Please reference this thread: http://www.terraforums.com/forums/sh...-Light-Amounts .
Just as as side note, if your nepenthes is growing entirely in long-fiber sphagnum, it may be too wet (especially as you keep it in a cup of water). Nepenthes generally like an more open and airy mix that is kept moist, but not wet. Low airflow and excessive water tend to cause root rot, which can very rapidly lead to the demise of the whole plant.