To me it looks like she has stepped in something that has temporarily colored her toes, but keep a check on it. I have seen areas of necrosis look like that after people have put vet wrap on that has become too tight.
I noticed it while bathing her & had taken a toothbrush to her feet, so it doesnt come off. It didnt appear to be sore. I didn find a case of bumblefoot in 2 other birds (grrr). could it be similar?
Its only on those 2 toes though..