I have three hybrids One is "nepanthes lovely beast" and is Nepenthes [(lowii × veitchii) × boschiana] × (×briggsiana × ×trusmadiensis). The other is "nepanthes vivid machine" which is Nepenthes (veitchii × platychila) "MT" × maxima "Tentena". The other is called titanic savior uses two parents in N. "Titan", our monstrously vigorous female N. truncata, and N. "Savior", an obscure clone of N. spectabilis.

I have them under spider farmer SF-1000s aiming for 400-500 uMol a day and they're in plastic containers with a lid and a rock bed with water. Humidity in my home is 65% but in my plant room with the windows open it's 42%. I have a humidifier going and hasn't seemed to help. I'm in the NYC area and humidity isn't a problem here, just strange that humidity is so low in my plant room. The lids stay open inside the mini terrariums but once I take out they close. I've read several places they do this to protect the fluid in the pitchers to stop from drying out. Turned the fan off to see if it can raise the level at all.

How fresh are your seeds?
Nep seeds germination rate drops off very quickly as the seed gets old.
Are you saying you have the seeds on a rock based soil?

I have only germinated nep seeds a few times.
I used a plastic container with no drainage holes. Use long fiber Sphagnum as my soil.
I keep the soil extremely damp. I placed the container in my kitchen near a south facing window.
Had no issues germinating them.