That will depend on exactly what is wrong with the hens. The short answer is "maybe."
Longer answer:
Some diseases can be transmitted through hatching eggs, and some cannot. Some diseases spread very easily among chickens, so the chicks could have gotten the disease after hatching, even if it...
That sounds pretty good. (I didn't really expect this to be the cause of your trouble, but wanted to be sure we weren't all missing something obvious.)
Since they are thin, maybe give them a bit more food each day, so they can always eat as much as they want and still have some left over. That...
Just to make sure: do they have access to unlimited food and water, all day long?
If you have any kind of automatic feeder or waterer, check to make sure it is working, not clogged up.