I wouldn't give her wormer, she probably looks pale from sitting 21 days. maybe wait till they are a little older before worming. can you give your girl some extra protein to see if that will boost her.
some canned salmon in water drained would be good or scrambled eggs even the chicks can eat stuff like this as long as they are eating grit.
When Smokey was broody before I gave Smokey and her chicks some scrambled eggs as treats and they loved it.