I'm sure you know that Hebs, and other primitives, tend to carry their fat internally, what they have of it. A normal routine condition score doesn't really apply to them. I would expect shearlings at this time of year to be a 2 1/2 or 3, and growing. You won't feel much fat on the spine, but you should not be able to stick your fingers round under the spinous processes. Gigots are longer than commercial sheep and less rounded to feel. I suggest you keep them on your good and varied grassland then reassess in late August.
Get a FEC done and treat if necessary. Don't give in by feeding concentrates as this will spoil the special character of the meat, and the presence of health-giving CLAs. You don't get cuts such as belly, neck, or big fat chops. We get two gigots, two shoulders, valentine (double) chops and all the rest minced for sausages, burgers or mince.
We send our shearlings off in mid to late August and get respectable weights, but they really do fill out over the summer. If you leave them too close to tupping time in November then there is a risk of tup taint, although we have only ever found that in a 7yo animal.