A body condition of 3 is ideal - not too fat and not too skinny. When you run your hand down a goat’s spine, it should feel like a tent with some meat on each side, sloping down towards the ribs. If the spine is buried in meat like the McDonald’s arches, that would be obese, but if there is no meat on the spine like a spinosaurus, that would be emaciated. It can be challenging to explain without pictures. When you looks at the underside of the tail, it should be a triangle with muscle at the base and tapering towards the end of the tail. A score of 1 would be like a rat tail with no meat on it, and a score of 5 would be like a sausage with meat all the way to the end although still getting thinner towards the end. Without knowing what breed your goat is, it’s hard to say whether 78 pounds is OK. That would be large for a Nigerian but very small for a standard size. If she is still nursing she needs more calcium and protein than what you’ve described. Alfalfa hay or alfalfa hay pellets are important, as well as a 16% protein goat feed. If you increase her protein, she should have no problem putting on some weight. I’m happy to hear your does have become more productive!