Is this horse being abused or neglected or something like that? and if so what can i do??

there are these two horses near mine and the are both teathed to the ground. they have room to move but i dont think it is enough. one of them seems really young. the have a bucket of water but they dont look clean at all there is a thick layer of dirt at the bottom. the one horse seems really nervous around people as if he hasn't been handled. the other horse has only one horseshoe ont his back hoof and it looks really small. it bends in way before his hoof does. alsoo they have buttercups in the feild and aren't they poisonous (only mildly i think but still it can't be good for them to be in eating distance can it??)
i am only a teen but feel strongly about this i wanted to ask peoples advise as i am not to sure on what to do please help me. NOT FOR ME BUT FOR THE HORSES.