There are a few possible explanations. Nutrient burn, light burn, pH imbalance, or expired/bad nutes. To me, it appears to be caused by a VERY slight nutrient burn developing. Some roots could have reached a hot spot in your soil(If you haven't started feeding yet). If you have started feeding, it may have been a slightly heavier feeding than what the girl was prepared for. Either way, it shouldn't spread too much further. If you're really worried about it, you may want to flush her.
I personally don't start feeding until the single-bladed leaves at the bottom of the plant begin to yellow. Because of this practice, I now call them indicator leaves.
In regards to your question about the yield; It's hard to say with autos, because they are usually shorter than photoperiods. In my opinion, it's all about genetics and how you dial-in the feedings. They're more sensitive to nutes/training than photos, so a lot can go wrong with an autoflower.
However, I'd say at this stage in her growth, you're well on your way to at LEAST an oz. Just make sure to keep her green, my friend ;)