Oily leaves?

I just got home from running errands and noticed that 2 leaves on my PurpleKush have oily patches on them. Any1 know what this could be caused by?

Are you sure it's not moisture, from where another leaf was sitting directly on top of it?

yeah, there are no there leaves there...???

Have you used neem oil? Did you use a lot of it?

never used neem, I think 1 of my CO2 makers was leaking, sugar water was all it was when I looked at it under my microscope