I would re-weigh, sometimes they are bigger than you think. Coccidia and heavy worm loads can stunt growth, as mentioned above. Sometimes the kids will not show many obvious symptoms, so a fecal would be good. I've never had LaManchas, but I raise Nubians and they often just grow slowly. They will continue growing until they're approx. 3 years old. That's why I wait til their second fall to breed, as I feel they need that full first year to grow and mature. I have a Nubian doeling right now who is a little on the small side. She is plenty long and wide, so I went ahead and bred her to kid as a 2 year old. Her dad and half brother both took a long time to reach their full height, so I expect she will get there eventually. She is quite healthy, just taking her sweet time to grow.