Your puppy moght just need to catch up on his shut eye from being so tired. But if he continues to be really sleep over the next few days take him to the vet if you think it is necessary.
I have a 8 month old shep/chow mix plus a shih tzu (3) and Schipperke (6) both of which I've had since they were pups. It's normal for puppies to have days of lazy with all the growing they do in such a short amount of time they sometimes need to rest. Now if she ate something different than normal or ate too much, had too much sun or heat. That could make her sleepy too. If her color is gone in her gum area, her nose is dry or she's panting a lot & can't cool down she could be dehydrated.
If she doesn't go back to biz as usual in the next day or two you may want to take her to the vet. Remember puppies are like us; sometimes we eat more-sometimes less the same goes with sleep and bursts of energy. I wouldn't worry too much. Good luck and protect the things you don't want her to destroy because teething is next.
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