Glad you were able to get your horse out of there! I would be putting the word out to people I know to stay clear of that place.
Also, good on you for taking photos of this. Never know if you may need some evidence.
Lack of water - nope. Both of the water tubs have wet spots. By looking at the photos, it's a warm, arid climate.
Standing in manure? - For all we know, the horses eat in those pipe stalls and get turned back out into a larger turnout. The manure appears to be dry - not fresh and piled.
Feeding on manure? - Who doesn't know a horse or a dozen that love to manure on their hay?
"Her horses" - The OP also stated these were NOT her horses.