Perplexed by our Nubians

Hello, I have hung around this forum on and off over the past few months, but finally joined today. I am posting out of frustration and perplexity with our Nubian does.
We have two milking Nubian does, standard size, and are getting about 5 pints of milk per day between the two of them on 2X per day milking. We bought 'Sugar' as a FF in April with two kids at her side and 'Hope' (about 6 years old) kidded in May with a single doeling. Both are rail-thin, and we are at our wits' end trying to persuade them to eat more. We run them with our sheep during the day in a rotational grazing system (FRESH paddock EVERY day during the summer) and feed them hay inside at night. It got to the point where they were all but refusing our home-grown hay (mostly orchardgrass with a little clover in it) and everyone says you need alfalfa to make goats milk, so I went out and bought alfalfa. They pick and root through it, eating what they want; but that seems to be very little. This is DECENT HAY, green, leafy, no noticeable mold. I've taken to feeding hay from three different bales, but it seems to make little difference. I clean it out of their feeder in the AM and feed it to the sheep, so they are getting new hay every evening.
'Hope' gets into this thing every summer where she quits eating grain, and this year is no different. Milk production drops sharply when this behavior starts. I give her all the grain she wants, she picks through it for awhile, then I take it away and give her oats and she picks through them for awhile. 'Sugar' is a grain vacuum and would jump off a tall cliff if she thought there was grain at the bottom. She was getting about 3 lb. per day (2 lb. goat feed & 1 lb oats), but I cut out the oats when I started seeing undigested oats in her stool.
We think we have some parasites, have seen some small roundworms in 'Sugar's' stool. I hit her hard (twice per day for a week) with diatomaceous earth and Molly's #2 formula. This, in connection with the alfalfa hay has helped production somewhat. I'm out of the Molly's, more ordered. If I don't see major improvement in 'Hope' I guess I'll go the chemical route and see what happens. Everyone says minerals are so important, so I bought Purina goat mineral last winter. The goats ate it for awhile, but barely ever touch it now. I tried sheep mineral for awhile, thought they maybe wanted a change, no joy. I cleaned out the feeder, thought maybe the cats or a rodent had been in there, same thing.
I read 1820 lb. on a 284 day lactation as an average for nubians, so I don't buy the "nubians don't milk" argument. Honestly, we would be thrilled with half to two thirds of that. I read about people running the kids with the mothers during the day and milking once per day, and it all sounds great--for the kids and for the people! But we expect these girls to work for a living, and it's honestly just not worth the effort to raise goats for a measly quart-to-three pints from two goats when we try milking once per day! But we would sure love to make it work!!
Something seems wrong, and I'm not sure if it's our goats or our management. (Both??) Both goats need to be culled (Sugar's udder is meaty, lopsided, and produces very little and she spends her days pacing the fence and screaming. My wife is sick of Hope body-slamming all the other animals around). I would like to hope for better things from their three doelings, but past experience leaves me with doubts. My wife raised sheep commercially for 30 years and goats on the side for the past 20. I have six years of experience on commercial (cow) dairy farms, so we are not total idiots at farming. But we are doing something very wrong with these goats.
This post is too long already. I'll wait for responses and post more information in follow-up posts if necessary. Thanks for reading!!