First of all, I am pretty inexperienced with sheep, having kept a small flock for a couple of years. So that may explain if this is a bit of a naive question.
I've got a mixed flock, Lleyn, Romney, Ryeland and "Kerry". Well I say Kerry, they were sold to me as such and I think they have a bit of Kerry in them, but also a mix of many other breeds. The Kerrys were my first and they are big brutes, easily 70-80KG and have always been very healthy. However, this year they seem to be struggling. The Romneys (reared from lambs) are like enormous puffballs of wool and the others seem fine as well, but the wool just doesn't seem to have grown back very well on the Kerrys and they seem to me to have lost a bit of weight. They have plenty of grass and "treats", i.e. bucket fed concentrates twice a week (I don't have a sheepdog so need them to follow the bucket when I move them). I had a fecal egg count done last week and it was <200 so the vets recommended no worming.
What should I do next? They are not struggling, so haven't called the vet out, just not doing as well as the rest of the flock. I'm going to get them a mineral lick today as I don't think that will do them any harm and might be helpful.