My 15 day old chick can't put weight on his leg

[chicken2020]

He was fine this morning but when we came to check on the chicks, he looked weird. He is using his wings for balance and hops from one place to an other and his tail is lowered.

This next photo is a photo of his legs.

There is no redness or swelling. What do I do to help him?

 

[chicken2020]

And she also does not seem to be pooing since there are no dropings in her cage