Will My german Shepherd be small forever???

hi...I don't know about the lepto, you might want to ask your vet that question and get an informative answer. but I did want to add that GSD's don't fully mature until 2 yrs of age. and their size can depend on what line of GSD you have as well. and males tend to be bigger, so you can't compare the two. if I may ask.....what kind of food are you feeding the dogs? this might also be a problem that you might have to address.