N. mad. is a somewhat difficult species in my experience. I have grown plants
for several years which did fine and had others under the same conditions
yellow and die right beside the healthy ones. In the case of the dead or
dying plants no live healthy root tips could be found on the plant (the roots
were dead). Whether this was the result of a pathogen (likely in Florida, the
fungi capital of the U.S.) or an incorrect soil media is unclear. I have my
plants on the floor of the greenhouse in a relatively shady situation,
however this is not what habitat photos show with plants out in full tropical
sun. From what I understand the habitat is a more or less sterile white-sand
area very open and hot, but this is the result of deforestation rather than
habitat preference.
Though it may further stress a plant in distress, it might be a good idea to
unpot the plant carefully, checking for live roots (i.e. black roots with
white or yellowish root tips). Repot in fresh media and drench with a
systemic fungicide in combination with Superthrive. Follow instructions on
both products carefully. If no healthy roots can be found, treat the plant as
a cutting and try to re-root it.
As a side note Atlanta Botanic Garden may have tissue culture plants of this
species available now. I have several of these and they seem to be an easier,
vigorous clone with nice red traps. T.C. plants in general seem easier,
perhaps because they have been spared a large pathogen load in their earlier
stages of growth. Anyway, these have thrived for several months with no
special care.
Cliff