There's large black spots on my N. Madagascariensis's leaves; It doesn't seem to be starting from either the tip or the base of the leaf. It starts from the "outer" part of the leaf though. Am I being paranoid or is this a problem? The plant is only around 2 inches high and sits about 18 inches from 4 32 Watt T8 bulbs + light from the west faving window the rack is set up against. I water it every three days - when the soil looks dry.