If it's too hot or dry, many Neps will stop pitchering to decrease their water needs. 80s aren't strictly too hot, but Neps from really high elevations really need a sharp temperature drop to rest each evening. In their native habitats, this nightly drop is an absolute rule; it happens every day, regardless of daily storms or decades-long heat waves. Ultra-highland Neps just aren't designed for anything else. If you can't provide those types of conditions, you'd be better off trying species from lower elevations. That said, it's very doable; you can rig a miniature refridgerator to cool your terrarium, or get a humidifier and pipe in humidified outdoor air in the night time to get a good drop. Air conditioners work, too. If you do a little searching I'm sure you'll find that people have overcome this type of problem before.
If the humidity drops to 25% when you turn a fan on, then you probably need a humidifier, or at least an open tray of water to moisten the air some. Or you need a smaller fan. Neps like good air circulation, but you don't necessarily need strong air circulation; a gentle breeze is more that enough so long as the entire enclosure gets fresh air.
Your setup may work very well for your other plants, but keep in mind that ultra-highland Neps are called such because they grow at elevations of 2000m+, where the atmosphere is thinner and there is less cloud cover. If I recall correctly, a lot of these types of Neps grow in clearings or on hillsides where there is minimal shade from overhanging vegetation. So basically, they may like things a little brighter than the average CP. Plants like Cephs, VFTs and Cape Sundews grow amongst low brush near sea level, so the conditions aren't quite the same.
~Joe