We just got back from our trip to Tahoe and went to pick up Brownie from the pet store that takes care of her when she is out. Unfortunately when we picked her up, they informed us that she has been peeing blood and has been very sick and not eating.
After bringing her to the vet, they discovered that she did not have kidney stones. I suggested to Steven that we get her fixed (she is still young) and when the doctor did the surgery, he discovered a tumor (which was removed).
We are now waiting to see what the biopsy says. Unfortunately female bunnies have a 50-80% chance of having uterine cancer, so we hope we addressed this in time.
Update: Brownie eventually passed away from due to complications associated with the cancer. I recommend all rabbit owners who have a doe spaid their bunny to prevent the onset of ovarian cancer.