When I was watering my orchids today, I noticed something new. Two of my phalaenopsis had developed a strange, blotchy section near the tip of one of their leaves. The section is a dark black/green blotch, with some brown/yellow blotching around the edges of the main spot. The orchids are placed in two seperate areas of the house -- one is in the main hall, which is the type with the high ceiling and a large window at the second floor level. The orchid itself gets plenty of light -- it is currently in bloom -- and is not placed close to a window. The second orchid is placed near a window in another room, but also gets plenty of light. I'm not sure what could be causing this. Any help would be greatly appreciated.