I am guessing a soil with some organic matter, especially something acidic like peat moss might be good. It also helps retain water. Maybe if 25% of the soil, or maybe a little more was of such material it the plant would like it? I am guessing, but if I find anything more concrete I will let you know.
Yes, these plants do have uncommon requirements. You should always keep the soil moist, and it should also be a bit acid. Other than that it likes bright light - perhaps yours could use a little more light?
Cool photos - I've added the plant pages so they can be displayed in the right places. Cyrtosperma cuspidisphatum and Cyrtosperma johnstonii...