This could be the start of scaley leg mites (SLM). Those will raise their scales and cause redness.
If you just have a few chickens, you can use vaseline to smother their legs and feet with. I'd do it at night as it's easier and also so that's left on all night long. Skip a day, do it again. Skip a day, do a third time. Then skip 7-14 days and do this whole routine once more. They take months sometimes to show improvement but at least won't get any worse in the meantime.
I say "if you just have a few chickens," because you should treat them all. If you have a lot, you might consider using Ivermectin.