A hay higher in alfalfa is definitely great, and most do quite well on just that, plus mineral. So if the rest are great, she might've had something going on. Some goats are just more thrifty than others.
A mineral block can lead to mineral deficiencies. They are mostly composed of table salt (NaCl) because it holds it together, with very little in the way of other mineral salts needed for the animals to be healthy. Because table salt is a limiter, they can't eat enough of the blocks to take in enough of the other trace minerals. What is best for goats is to actually offer a loose goat mineral. Loose minerals have very little table salt, but higher amounts of zinc, copper, selenium, etc. Loose minerals are offered free choice, in a dry place where they cannot be soiled, and topped off as needed. I keep a pan attached to the wall for them to lick up as they needed it.
Resistance is frightening. And sometimes it can be hard to avoid. A lot of areas already have a lot of parasite resistance going on. Most fecals are fairly cheap (unless my vet is more reasonable than most), and are a great tool to ensure anti-parasite therapy is effective. Worming when actually needed, with the proper dosing schedule, dosed according to weight, and with the wormer that works against what they actually have are all important. Plus a follow up fecal to make sure it did its job.
