Its worst when you think that you are doing something right then they go and die on you, last spring I had a bunch of bought in welsh ewes that I though looked "itchy" so penned them nice and quite, gave them cydectin 2%, crovect and Hep P while at it, I got back home thing that went well, 10 mins later the landlord rang to ask why I had left 6 dead ewes in the field. I went back and the must have died as they ran back across the field.They do it out of spite