unhappy horses get skinny?

We used to keep one horse at a place near a dromedary and another horse in the sameplace as a young but not so well kept horse. Both of our horses went skinnier while they ate normally and healthy.
Now we are able to keep them both with other horses each in a room of their own without halter without strings so they can move freely in their space, they can watch eachother over the halfclosed door and amazingly after two days they allready look healthier. I am so happy, because I was so worried!
Anyone a similar experience? (Ok without the dromedaries).