I doubt if you have good grass. You might have a lot of grass, but the nutritional value is likely to be low by this time of year. We're the same - lots of grass.
We're feeding Farmgate All Stock Pencils at about 0.5kg per ewe while the tup is in (ie until tomorrow). They also have a Crystalyx Standard Hi Mag lick. From tomorrow, they will be in a different field with a shelter, with ad lib hay and the lick. We'll cut down the pencils over the next week or so. That will be them until 6 weeks before lambing if they are carrying twins or the weather is bad.