Fox- Mange or moult?

I'm getting a little concerned about our resident vixen... she seems to have lost a bit of weight, along with most of the hair on her tail.

I'm not sure if she's simply shedding in preparation before re-growing her winter coat, or if this is something I need to be worried about.

I'll try and get a photo of her on the trail cam tomorrow... looks like I might need to contact a fox charity again.