Yes, 2 summers ago, Daisy went on a complete eating strike and it was just as you described -- it happened over the course of about 2-3 weeks. At the beginning, she would eat only treats and eventually not even them. The absolute only thing she wanted to eat was grass, and one of the vets we saw told us to stop her from doing that because it was so hard on her digestive tract, especially since she was eating nothing else. We took her to the vet several times and I think he thought I was exaggerating that she wasn't eating a thing. He eventually kept her overnight for 2 nights and lined up 5 kinds of canned dog food in front of her and she wouldn't even sniff a single one.
We ended up doing x-rays, ultrasound, and barium series before it was all over. They never really did find out what was wrong with her, but eventually just called it gastritis (or gastroentiritis, I don't remember.) The concern was that she had a blockage, but none of the tests showed any evidence of that. The last time I was at the vet during this period, he gave me a feeding tube/syringe thing and said that we had to get her eating, one way or another, even if it meant force feeding her. So I decided to try Satin balls, and that got her eating a little bit, and then more and more over the course of several days. Then I had the chore of switching her back over to regular dog food. You can look up the recipe for Satin balls on this forum and read more about them. I have to say they really did the trick for Daisy, but you need to rule out possible serious causes for the lack of appetite first.
So I would definitely take her to the vet, in case there is a blockage or some other problem. If her abdomen/tummy feels hard, that is one indication of a possible obstruction, along with vomiting and stopping pooping. Daisy never did those things (except the lack of poop, but of course that was because she wasn't eating), but he eventually ordered the x-rays, barium series, etc. because he just couldn't figure out why she wouldn't eat.
We had gone on a trip in June and right before we left, she had become very picky eating. We had a dog sitter here for her, and I think that stressed her out, and I think the sitter was giving her all treats because she was so scared about her not eating. At the time, we were giving her the Smokehouse chicken breast jerky treats that I've read terrible things about since then, so I think those were contributing factors.
Daisy's fine now and has been an eating machine ever since. I spoke to her breeder several months later and she said she had a dog that did that a couple of times and they learned that they just treated the symptoms and it eventually went away.
Good luck and let us know what the vet says (or if she starts eating on her own, let us know that, too!)