There's no genetic, environmental or situational connection that I can see. The vet looked at 3 of the 4 calves today and felt the two younger ones were two different problems yet than the others. One he said looked like a circulation problem caused by bacteria that the calf will probably lose his feet (and life) from. The other he thought may be a navel infection, however I'm skeptical of that. It's too similar to the others. Time will tell I guess.