Spots and rot in Dendrobium

[Leafmite]

How are you growing this? Are you growing it under lights? You see, what you are showing in these pictures looks quite familiar to me. :|
I have a little experience with these after killing a Microchip and the two 'parents'. I actually replaced the Microchip and, now that I seem to have gotten the culture down, I may go ahead and replace the other two.
Here is what I did wrong:
I grew these directly under my T5HO (four lamp, four foot) lights, didn't water often enough, it was cold at night and there wasn't enough humidity. The lights were pretty close to the plants.
After I killed them all, I mentioned to one of my fellow OS members about the experience and was told to grow them in shade, give them good humidity and to keep them warm. So, this time around, I have the Microchip with my Phal bellina and Phal violacea in a tabletop Ikea greenhouse, right next to the lights but not directly under, sitting on a heat mat. And, this time, the leaves do not look like what you are showing but are perfect. Even better, it initiated spikes and has been in bloom.