Had nearly the same with 5 sets of twins born a couple of days before due date. The larger lambs are fine but all the smaller ones died. Don't think they passed the black plug...spotted another later on with same symptoms, hunched, big belly and a clean arse. Flushed it out with a syringe full of warm soapy water and a couple of hours later it was fine. Ewes all had colostrum and good full bags...can't work out why that would happen to the lambs, anyone got any ideas?Last Sunday (2 days before the due date) I had 2 prem trebles and 2 doubles and within 12hrs I had 2 live lambs out of 10.