Mod version 2.1.0
Despite the in-world fluid having a texture, the fluid has no texture inside jei (there's only an ectoplasm texture in the resources/assets/netherexp/textures/blocks directory (adding a texture to the fluids directory didn't change anything so this likely isn't the cause unless there's a nonsensible id that I didn't check))
There's also no language entry defined.

i knew about the language entry, but uh the texture is perfectly fine in EMI e.g. so that might be a jei thing

I have no idea what's causing the texture thing on JEI but the lang file has been implemented