You can worm just her or the new ones, but Corid is fairly safe, so all of the new chickens could get it as well. For bumblefoot, I would soak her in warm Epsom salts daily to soften the scab. Plus post a picture of it. You might then want to either remove the scab and squeeze any kernel of pus out of it. Or you can do the bumblefoot surgery when she is feeling better. Using Betadine and sugar in a paste or Prid drawing salve on the scab under a bandage for several days is another treatment option. Here is a link to read about different bumblefoot treatments:
https://the-chicken-chick.com/bumblefoot-causes-treatment-warning/
https://the-chicken-chick.com/bumblefoot-causes-treatment-warning/
