If you have blue kote then spray it on their backs. since they are chicks I would give some kitten chow, since they are normally smaller pieces. Keep watch of them and if they continue to loose feathers then I would seperate. But I would try other methods before seperating them like I stated...
Try giving you chickens some dry cat food. This will increase their protien which is most likely the culprit. Do this for a few days along with their normal feed. Then give it to them once a week or every other week. You will know if they are getting enough by whether they are picking at...