With my eggplant, when it gets the green or brown stripes or spots, it's from what i assume to be blight. Here in MD that's normally not until the end of september or into october, but this has been a god awful year so far for tomatoes, so maybe i'll see it earlier in my eggplant. Eggplant so far has been doing very well here, but with the cool temps we've had lately, not sure how long it will last.

Ill have to take a picture. I don't think it is blight as the plant is very healthy looking. Ill post tonight.

It is also possible that your seeds were crossed with a white or striped eggplant. There are quite a few striped eggplants in the Black Beauty class and the market is not very diligent in providing pure OP seeds.