If they aren't starving them, then why are all the horses at this stable, including yours, underweight? They certainly look like they have been on poor quality or not enough feed. I'm not criticizing you dear, just the fact that if all the horses are thin, its lack of overall care. One thin horse in a herd might be a vet issue, or being bullied out of food- but if all of them are thin its a management issue.
Accidents happen- but any normal person puts a fence around a pool- to prevent children and animals from falling in.
Spent a whole hour today laying in a pasture, waiting for a sparkling vampire to show up. Alas, I woke up and looked over, only to find a mound of horse crap. Sigh.