It could very well be pano (growing pains). My puppy is almost 7 months and started experiencing the same thing. I've had him on adult food with a lower protein since 16 weeks and he did fantastic. I recently switched him to a high performance dog food and he started limping. The protein level in his old food was 26 %; when I switched his food it increased to 30%. I just switched him back. Still going to the vet tomorrow just to rule anything else out. Check your puppy's food for the protein level...hopefully that is it. It temporary, but painful for them. My guy also had a decreased appetite. I have him in the crate for some rest so he doesn't injure himself hobbling around. Good luck!
Thanks for your input! Her current food (which we've been feeding her for a couple months now), has 26.58% protein listed for "As-is Basis" and 28.53% listed for "Dry Matter Basis". Not sure which figure to go with... we mix it with a little bit of pumpkin too. But there haven't been any recent changes in anything she eats.
Will put her in the crate if we have to, but so far today she seems happy resting (she did have an exhausting weekend)... plus I caved and let her sleep on our bed for the first time... couldn't help it.
now I've learned, once she's on the bed, she doesn't want to move...