Bunny Rabbit has growing Scab on Ear. ?

I took pictures of the scab on my bunnies ear. To see the photos please go to the photobucket website link I provided. I also attached 3 pictures as well.
   
My bunny rabbit, Floppers, has what appears to be a scab on her ear, I cannot exactly figure out what it is or what I should do.
   
A few days ago I noticed a circular ring on Floppers ear.
   
The next day the circle grew into a black rough bump. The rough lump on her ear was bigger than the previous days ring.
   
Today the black rough bump looks like it turned into a Scab. Today I can see some pink.
   
I cannot figure out what could have caused this or what this is?
   
Floppers history:
   
Over the summer Floppers was very sick. her head was tilted and her tail/bottom was very wet and dirty. The vet said she believed Floppers had Ovarian Cancer. That same day the vet called us and said Floppers might have a Urinary Track Infection (UTI) caused by a parasite. The vet gave Floppers 2 shots of penicillin and we fed Floppers antibiotics twice a day for about 2 months. Once Floppers got better we put her back outside with her family.
   
Now Floppers has this scab on her ear. Do you think Floppers may have another parasite?
   
If you have any ideas, please share them!
   

   
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