In my experience, a little allstock is plenty for little primitives. Ewe nuts will be higher protein, more suited to commercial high performance sheep.
But the very best thing for making milk is grass! And they don't need to adapt the bugs in their rumen to digest grass... So we feed a grass nut if the actual grass isn't lush enough for our multiparous mummies.
I've fed alfalfa to Jersey cows, they love it and it helped them make milk. So the alfalfa nuts might be good. You won't use more than a bag if you're just helping out a trio of primitive twins mummies, will you? 1/2lb per head per day is quite a lot for that size, 25kgs would last over a month, the grass should be well growing by then?