Grass-only milk goat looking skinny

I had thought that a dairy goat that wasn't fed grain or concentrates would just make less milk but mine is getting skinny looking. Her pasture is lush to overgrown with lots of things goats love to eat. It's really understocked at the moment. She's got two kids that are fat and healthy and growing fast, and I'm milking her daily in the mornings, enough to meet our needs for the day, without separating the kids from her so far (they're 4 weeks old) even at night. She's a registered ADGA Nubian mix, so she's been bred to be very milky I guess. I have treated her for worms but maybe my dewormer is losing effectiveness or she's got something it doesn't cover? Or is it normal for a very milky goat to look thin? I can feel her ribs tho they don't show and her sides go in by the hip bones. Her fur is coarse and rough, tho it's always been like that. I give them goat minerals, kelp, and baking soda and she gets a handful of sunflower seeds morning and night to get her to come in. For milking I give her cut branches of bushes I want to get rid of anyway and she's happy with them (she often eats them in her pasture as well). She acts perky and normal, and the FAMCHA is normal, very slightly pale but not too bad.

I looked up body condition scores for goats and she's a 2.

Is anyone here doing pasture-only dairy with goats? How is their body condition scores? http://www.docstoc.com/docs/84279289/Body-Condition-Scores-in-Goats

I went out again after reading the BCS scoring and she's not skinny really - she's between 2.5 and 3. I think she looks worse first thing in the morning because there's no water in the goat shed so she's a little dehydrated. Do most people keep water in the goat shed? Mine tend to poop in it or spill it and wet the bedding. Or both.

I would try to have water available at all times for a lactating animal. That is their most important nutritional need.
Heavy milkers should not be heavy fleshed, so I think you are right about her body condition being appropriate.
I raise grass-only dairy cows, but my neighbor has grass-only dairy goats and they do great. Keeping the mineral supplements available like you do is a good insurance policy.

Rotating your animals through the pasture to facilitate adequate rest periods will be really good for both the pasture and your goats. I know it seems tricky at first, but once you figure out a system, it is totally worth it. One easy way to get started is to get four lengths (whatever size seems appropriate to your situation, maybe 80') of electro-netting and a solar fence charger. Make a paddock with two pieces, then when it is time to move the goats, set up a second paddock with the next two pieces, so that you can just open up the end of the first paddock, and the goats walk through into the second paddock. Then take down paddock number one, and set up paddock number three with that electro-net. Hope that makes sense, it is quite simple in practice and doesnt take more than a few minutes each day. This system will nullify any concerns about parasite loading in your pastures.

Interesting thing about dairy quality pastures, is that neither lush nor overgrown are ideal. It sounds like you are understocked, which is certainly better than overstocked, but still will cause problems with animal nutrition. I would reccomend reducing that area you are grazing, and rotating it with fencing. You ideally want grass that has 4 leaves and is not yet heading up. Legumes should be just starting to bloom. A good way to know for sure is to use a brix tester to know what the energy levels are in your pasture plants. Overgrown pasture will be suprisingly low in energy, not really adequate for a lacating animal. Long and overgrown pastures can be deferred for later grazing when your animals are dry. The massive amounts of builtup biomass will then serve you well. Three good modern books on the subject are "Management Intensive Grazing", "Grassfed to Finish", and "Quality Pasture".

hope that helps some, good luck