We successfully lambed for the first time in March with 16 healthy lambs. All was well until about a month ago. We noticed that three of the male lambs were much smaller and not thriving. Their horns were not as developed and brittle and they were scouring. They have been heptavac'd and wormed and trearted against fly strike. One died at the weekend and I'm concerned about the other two. All the girls and the rest of the boys are very healthy. Any thoughts or advice much appreciated .