Fleeces will also tell you when cobalt is an issue. If the fleeces are tender when you shear, then there is likely to be a cobalt deficiency.
Our sheep now get an annual mineral drench, which I do after tupping. One or two drenches annually of a good chelated drench will do far more good than more frequent drenching with a cheaper, non-chelated drench.
Like many on this forum, I now use JG Animal Health.
Linky. If you are in the north of England or southwest Scotland, Carrs' Ovithrive is much the same.