Many times weakness stems from vitamin deficiencies on the breeder birds part. If they were lacking certain vitamins, the chicks hatch weak. Not always, but many times this is the case. Sometimes improper incubation temperatures can cause leg issues and weakness as well. This is why I would keep up with the Poly Vi Sol. Weakness can take a couple of weeks to over come. Just make sure she has complete access to food and water at all times. Set her down right in front of a pile of food and you can use a jelly jar lid as a waterer for her. She can lay there and eat and drink all day long.