I have an indoor PC grow going(http://forum.grasscity.com/micro-grows/754503-first-pc-grow-w-pics.html) and after about 2 weeks I have a really bad white powdery mildew problem in my house. In one of the grow books I have, it is said to be a high humidity and/or poor air circulation issue. Only thing is, my humidity hasn't been above about 50%(avg 35-40%/ temps 60-73F) in the PC case and the room it is in. While the rest of my houses humidity is around 25-35%/temps 60-67F(live in a cold climate area). The white powdery mildew is showing up only slightly on the walls of the PC and not really showing on the plants. I checked them with a jewelers scope and other than the bottom leaves yellowing, the other leaf sets look a healthy green, no white spots/blotches. WTF? The main problem is this white sh*t is showing up on everything plastic in the house, i.e. cups & bags, and other clear surfaces. I have wiped everything down and have taken out my intake fan on the PC case, other than that I can't really find any solutions at the moment. Some help would be greatly welcome!
Your temp/humidity sound good if its not really on the plants then i would think ur fine for the moment keep the walls clean where u see it.
Did you just start using a humidifier? I used to have one of those cool mist type and had the same problem. My water is hard and when the mist dryed out in the air it would leave a white film of minerals on everything. BTW, I used it for breathing, not growing. Just a thought.
Yeah, I feel like an idiot. It was more than likely the cool mist humidifier I just picked up. Brought it back to the store ASAP. I did spray the plant down with some organic garden fungicide, though, just in case. Thanks for the info.