Is It Normal For 5 Month German Shepherd To Have Weak Legs 15 Weeks White German Shepherd With Weak Back Legs?

15 Weeks White German Shepherd with Weak Back Legs? - is it normal for 5 month german shepherd to have weak legs

My WGSD a weak hind legs, since the day I was up to 8 weeks, my breeder says it is normal and should improve if they are 10 weeks old. It is now moving normally, but they can not even jump on the couch, and it works very much slower than the golden retriever who is 5 months but is much slower than it once, you can not really skip. Is this normal for his age, German Shepherd puppy?