Not enough milk!

[Taffy]

Don't give up hope! I have a friend whose doe had a nasty case of mastitis in one half of her udder. The udder was small while the other half was producing copious quantities of milk ( on milk test). This year the udder started producing milk again and her udder returned to the gorgeous udder she had previously.

Yes, Petunia's "full" side will shrink in size when she dries up.