well since no one else is going to answer i guess i'll throw out some of my vague ideas. long hooves can be genetic or environmental. if the cows arent related you can rule out genetic. they can get long hooves from being on soft terrain that doesnt wear down the hoof properly. or they can get long hooves from being foundered, but you say theyve been on grass. do you know the cows history or did you buy you them from someone? sometimes it takes a while to show up. another possibility is that they got into the feed room and those three engorged on feed... foot rot can also make them do like that but i wouldnt think 3 would. most foot rot foot abnormalties ive seen were more like a club footed hoof, as the cows dont like to walk on their heel. however, they say foot rot usually occurs between the two front claws but it never does here. certainly that could lead to elongated hooves that cross over eventually. another thing you might want to check for is corns between the claws. if the cows are worth it to you, you can probably get their hooves trimmed.i never have, bad feet go to the salebarn. clear as mud?