The no grain part could be the problem for the younger heifer. Your cow looks good although the angle doesn't show much. The two year old is heavy for a Jersey (assuming you used a scale) and I would say it grew good although her hind quarters look small. That could be a optical illusion because of her large stomach. Her large stomach (capacity) had me assuming that she was from eating a lot of forage and little/no grain, therefor the question.
The younger heifer could have been put on hay too soon. Calves need to develop a rumen. For a dairy that feeds grain that means getting them on starter quickly to develop the rumen. Most studies say that the rumen doesn't delvope as quickly on a hay diet. Many dairies (mine included) don't supply hay until the heifer is past weaning (30-50 days at weaning) and eating a steady amount of grain/starter. The 100% grass dairies (mostly organic) usually get around the grain by feeding milk for a longer period of time, up to six months. I have heard of costs up to $1,000 just to weaning age for an organic dairy that weaned at 6 months using only their own organic milk. That's around my cost to raise a heifer for 23 months at calving! Beef calves are on momma for a while as their rumen develops.
As I write all that, there could be other problems. I had a heifer that I recently sent to the auction at 12 months old which was raised the way I describe above. She somewhat looked like your calf, unusually hairy and a somewhat large looking head compared to her body. She was underweight and wasn't likely going to amount to what I want for my herd, so I culled her.
She just turned 1 in March
