Could just one pig in a herd have mange?

At first I thought my sow was just blowing her coat - she was getting bald patches. But the hair loss has continued for over a month now and it's not growing back. She doesn't appear itchy and I'm worried she may have a nutritional deficiency. She's got 10 week old piglets that she gave all her fat to - now they're fat little sausages and she's skinny and balding. I keep increasing the feed. The weight is coming back slowly but the hair isn't.

I've combined all of them into one herd, in preparation of them going on pasture when the grass comes in. All the others are very healthy looking. She was always easy to maintain on just forage and soaked oats. I caved and got her commercial "sow and pig chow" from the feed store in case her diet was deficient in the winter, and they get all the scraps and spare eggs. The other pigs are all looking very fit, and her piglets are really growing rapidly and are very very fat.

So am I doing something wrong or is this normal??

I've read pot belly pigs do lose their hair once or twice a year then grow it back. I've read the sows lose condition when nursing because they can't eat enough fat to make up for how much is going out in their milk, so their body condition score can go from 3/average to 2/thin. Mine went from 4/fat to 2/thin. Her ribs aren't showing but she looks bad to me.

Sometimes I just worry too much but it's better, imho, than letting something go then finding out I was doing something wrong.

I've got one cow with some bald patches that I thought was from over-grooming by her very loving calf, but the two together now have me concerned that they may have mange. Still, after reading about how overuse of dewormers is killing off dung beetles, I'd rather not worm them unnecessarily. I had a stool sample tested and it was negative for parasites a month ago (I know, mange is different, but my point is they don't need to be de-wormed).

I am not sure at all about whether it's mange or not but if those piglets are not weaned you should separate them immediately from the sow. They are well past weaning age and often times the mother cannot do it herself... they are very persistent. If they are still nursing that is likely the problem or the root of the problem (she could be very weak and susceptible to desease.) Also you should separate the one who is sick from all of the other pigs. Any sick pigs should be quarantined or you risk the whole herd being infected. She will be very happy to have private space away from her piglets. Just keep her separate until she dries out and seems healthy... yogurt or kefir in her diet would help quite a bit.