This is a small singalana that had been growing quite well until about two months ago. At that time, the leaves started getting dark patches on them, and it hasn't pitchered all that well since. The new leaves are fine, but after a couple of weeks they show this symptom - as you can see in the picture. I thought it might be mites of some sort, but I honestly cannot see any at all - and tapping the leaaves over paper yields nothing.
I'm thinking it's 'sunburn'. It sits about 6 inches or so below 40 watt daylight flouros (there's a total of 4 of them - only 2 are directly above the plant) for about 15 hours a day. Well drained media (here recently watered - it's not kept wet), temps of 60F - 78F, 75%-90% humidity.
So - any idea what this may be? Is it light levels, or some type of fungus/parasite?