Soft green goat pellets

We have 2 older goats with our sheep out on pasture, no supplemental feed other than minerals (which I just started feeding a few days ago). We have had them for about two months. The 2 goats don't seem to be putting on weight, their ribs are just barely showing. Their pellets are very soft and very green. They have good energy and eating well.

So what's going on? Do you think their too skinny? Do we need to worm?
Sorry for the silly picture, it's the only one on my phone. But it kinda shows her ribs.

Thanks guys!

Of course, it's hard to say just from pictures. She does look underweight, though, and soft green stools mean something digestive is going on.

Goats are browsers, not grazers. They don't eat grass--or not grass and similar plants alone, like sheep do. Goats go after brushier/woodier feeds that tend to have lower moisture content and higher cellulose and other indigestible fibers than grass has. If you don't have enough browse on that pasture, they might need a little hay to keep the right fiber balance.

Have they been ruminating (cud-chewing) properly? Have you found any regurgitated boluses (little wads of chewed-up plant material, usually smelling very strongly) lying around their spaces?

Good observations from Libbie Hawker.  
And, if you think they may have an overload of parasites, it is best to have a fecal exam done first. in order to find out what sorts of parasites may be present, in order to use an appropriate dewormer.