Well, I hope it isn't due to low light, as the affected plants are showing some nice color under teh bulb, so I'ts probably due to either high umidity or low air circulation, since from time to time I take the plants out of the tank to water them ,and inevitably some will spill on the bottom of the terrarium and sit there. I also consider mysel pretty diligent in removing dead matter from the plants, and I frequently clip back dying leaves. I have a small fan I can use to increase circulation, how long should I leave it on for? Also, what brands of fungicide do you recommend? I tried looking for some at my local Lowe's (regretably the only thing resembling a garden shop within walking distance) and I didn't find any fungicide. I'll try to make another trip out soon.