It sure wouldn't hurt to try him on some liquid B complex. give him a place where he can rest and not be moving around so much so he does rest. Also, water therapy is good because it takes weight off the leg but keeps the muscles from getting weak.
We have to eliminate so the first would be a niacin deficiency which Pekins are known to have. So do the liquid B complex and rest and see how he is doing by middle of next week Hopefully, you'll see improvement .You'll want to keep him on the liquid B complex at least a week after recovery, then switch to Nutritional yeast daily over their feed. 1 Tab to each cup of feed. Or you can just keep using the liquid b complex.
https://www.backyardchickens.com/threads/niacin-deficiency-in-waterfowl.1367557/