Have a look here...
Guinea Lynx :: Hair Loss
The first two links are mites and fungal, but some fungal infections does not look as bad as that, I have a sow who is nearly 4 and she suffers with a fungal problem. Do you noticed any large pieces of skin on the end of the hair when you stroke her?
BTW the website is an American based site so the information may be slightly different for UK.

Emma x

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