I have several vivariums as I am trying my hand with dart frogs, t5's are usually more than enough, do you monitor the temps in the soil as well?? An under tank heater may solve that issue. As for mh light fixtures they will raise temps so as was stated previously a fan will have to be added,but this is a good thing as most vivariums require adequate circulation. I am not an expert on carniverous plants but my bromeliads ferns and tillandsia's do well....Yes I am aware that broms are sometimes considered carniverous.
As for the light fixture itself I had no problems with mine and have bought from seller before. Oh and do you have screening on top of your tank? Depends on bulb type but you might over cook your plants if you arent careful as well...Misting system??
check out this link.
http://www.vivariumforum.com/community/