One of the girls has started getting bald patches around her rear half, along her back, the base of her tail and her back legs. Her sister seems fine. A friend suggested it might be ringworm, but in that case wouldn't they both have it? Also they've both been dewormed and deflead recently.
If it gets any worse I'll take her to the vets, but I'm hesitant to stress her out if it's something that can be cleared up with time or some simple method.
Any ideas or experiences?