Unknown Skin Condition or Ringworm?

[Skiff]

So for the last few months one of my girls has had some kind of skin condition, her fur has been thinning by her back legs/abdomen and is quite itchy, inflamed and crusty. My first thought was ringworm as one of our kittens had it late last year. The cat was treated fine and anyone that caught it from the cat now has no signs so we assumed it was gone, then Jinx started losing her hair. 

When I took her to the vet, she was not certain that it was ringworm as neither Minx nor Poro show any symptoms at all and they all cuddle up together nightly, so she gave me some anti-biotics for her to take in the meantime while they waited for results on a culture but these didn't have any effect. When we got the results for the culture, the Vet did not seem confident, but said that there were small traces of ringworm and gave me some shampoo for her (Malaseb). 

As for Jinx herself, she is just happy and mischievous as usual, just itchier. I don't think it is ringworm because everything I read about ringworm says it is highly contagious but nobody else in the house has it, nor do any of the other animals. I have linked some images here.

Does anyone have any idea what this could be?

[Corvidophile]

Could be a food allergy popping up, they can form at any time. Usually with adrenal balding there’s no crustiness. What do you feed them?

[Skiff]

I feed them a raw diet made up of Bulmers complete mixes, now that you mention it when I got their last batch a few of their usual mixes were out of stock so I had to get a few new ones which they generally don't seem keen on. I have to order the next lot this week so I will see if that makes any difference. Is there any way to confirm a food allergy? The crustiness is the reason I don't suspect adrenal too.

[Corvidophile]

You’ll have to try an elimination diet, but it’ll be slow going at this stage of irritation because I’m sure the scratching is due to the crustiness, and the crustiness gets worse from scratching. It’s a bad cycle to be in. Start by removing the newest protein additions for a few weeks, to see if there’s any improvement. You can give a warm water bath to try and soothe the skin, but don’t use any soap, that’ll just make the irritation worse. Oatmeal in the water might help (put it in a sock so as not to clog your sink/tub)

[Skiff]

So I have been keeping an eye on this, I've got the fresh batch of food and excluded the Turkey (which was the only new thing in her diet) but there's no change. Something I have noticed though is that her back paws look quite red and sore and her nails are thickening though her front paws, are unaffected, whatever is wrong with her, it only seems to affect her from the waist down (not sure if ferrets technically have waists but you know what I mean lol). Is there anything that can affect her paws, claws and skin in certain areas?

[unclejoe]

it could be a fungal infection. (ringworm is a fungus) It would be a good thing to get her to a vet.

[okojosan]

Have you changed any laundry detergent or started using a new spray cleaner lately?

[Corvidophile]

If the nails are thickening I’m changing my opinion to fungus as well.