What disease does my nep have

[Z_Y]

I'm curious if anyone has any opinions on what disease this leaf has? It's on one of my N. veitchii, I haven't seen it on any other leaf nor the newest leaf, but I noticed it was growing in size. It started as a small patch near the upper right side of the image. The affected areas look dry.

I'm wondering if anyone has any reporting on if this is some sort of fungus or if it's damage from high light conditions?

Thanks.

 

[Camden M]

I would guess it’s some sort of fungal issue