I would not keep taking them out and putting them back in with the hen- if they are poor-doers, take them out and keep them in a brooder full time. My main comments would be is if these chicks could not hatch on their own and they cannot walk normally now- this is probably related directly. To hatch, they need to first pip, then rotate in the shell to pop off a circle of egg shell. They could not do this, as there is something wrong with them- likely with their legs- as they cannot walk now. Spraddle leg or splay leg can be a heritable problem or incubator problem. If you want to keep these chicks, you need to address this problem, if they are not dramatically getting better on their own. Chicks with spraddle/spay leg kind of look like they are swimming with their legs, and cannot stand normally- sometimes it is one leg, sometimes both. Most people who breed chickens will cull these guys- as it can be heritable- you don't want to promote this gene in your birds if you are hatching eggs! If you just have pet birds- you can try to correct this with tape 'hobbles' to bring their legs underneath them in a more anatomical position- but you need to do this early, not weeks later after they have started growing. A bird that cannot walk, will rapidly get sores on it's hocks and chest/breast bone as it grows larger. So if it does not correct/get better- you need to humanely cull the chicks.