On occasion I will have one that does this. I give them some Ensure and treat with Tylan like its a myco flair up. It doesn't seem to be infectious. Tylan shouldn't be given with milk products, so I give one in the morning and one at night, probably still not ideal, but what are you going to do?. The Ensure really helps get the weight back on them. I need to look a little harder for a non dairy one. Maybe they make it in soy??
Wolfyhound soaks her mazuri in the Ensure so they don't knock it over and spill it.
This seems to happen with my really old breeders and girls bred a little too young. One of the drawbacks to harem breeding.