The other thing she could have her water checked for is Manganese... Its similar to Magnesium, but if she wants to raise fry, this is Important to check for.
One summer when it was really dry our well got low, then later we started getting an orangish brown tint to all of our white clothes that got washed... we found out the Well had had some Manganese near the bottom or whatnot, and we basically had to tyedye all of our old whites since it wouldn't bleach out.
The reason I mention the fry is, both of our broodmares were pregnant at the time, and BOTH foals were born with a Club hoof, (Where a tendon is shorter/tighter than it should be, making the hoove angle too vertically and putting extra pressure on the joints.) They've never had Clubbing in their ancestors, and after we moved they've had foals, and those ones were fine too. So we think It might have been the water.