I'd advise trying to get a diagnosis, or you risk having to treat them several times. (Ask me how I know

)
If you take a fresh skin scraping (with the wool you scraped too) to the vet they should be able to see what the problem is, and prescribe the appropriate remedy.
Could be (probably amongst other things) scab, biting lice, sucking lice, keds, or no beastie just weather related / mineral deficiency...