I'd start adding niacin to their feed or water. Leg issues are usually a sign of Vitamin B deficiency and can usually be easily corrected with added niacin.
If your other one isn't eating - is the crop full? It shouldn't be if they've not eaten.
When feeding anything other than their...
At a month old and being inside, they likely won't need supplemental heat anymore.
Are you adding niacin to their water or food?
What is the protein % of their food. The first few weeks when they are really growing like weeds, a high protein is fine, but beyond that, it can cause some issues...