I have six berk feeders that are about 150# at 5 1/2 months old. One of the barrows is wobbly. He gets up and around but sits frequently and when the others bump into him he is easily knocked over. He has a difficult time stepping over the 2x6 at the gate to the pig moving pen. They are rotated in pasture and fed 16% ground corn/bean meal with minerals. He has been like this for a couple weeks and is not getting worse but not getting better either. I've read mineral deficiency can cause joint problems but they have that added to their feed. Any ideas?