Never had it before. Was probably going to wean my best group of lambs. 300 lambs in the group. Nice big females to select from. Then about 10 days ago I noticed one or two. Since got them in to worm/wean. About 60 in the mob now. Some real bad swollen faces. Lambs have gone backwards 10 fold. I weaned them and split them up ones with and without. To try snd stop it. Now I hate going to check on them as look ugly as sin. Advised to let it blow over. Have put salt licks out. Any other advice?