Twin lamb disease is pregnancy toxaemia, Hazel. She has been avoiding eating the ewe supplement because in her huge state she didn't want to be jammed up between the other ewes. The grass began to go off seeing she is not supposed to be lambing this late, and we've had stupid cold weather this Spring. Oh, also I have seen her go for the mineral block, only to have other sheep with their lambs crowd her out. Not to worry, she is eating again now and may get some strength back.
Horned sheep can be a headache, quite literally, for other sheep seeing they like to butt heads, Barkingdog. I actually had one wether, no horns, kill a ewe by head butting her too much.