Amber it sounds like you're giving your plants too much humidity or they are too wet. While many cp's like high humidity, I find giving them good air circulation is also beneficial.
Keeping the potted plants in a tray with live moss can help increase humidity without having to have them totally enclosed.

I am not a fan of terrariums for Carnivorous plants, there is no need to put them in one. If you are starting seeds then putting them in a green house environment to start until they germinate is find but once they are up they need fresh air and should be taken out of the terrarium.