Chick has blackened toe

[Lionbee]

I have noticed that one of my chicks has a black toe. It doesn't seem to be getting any better and now I see a little black on a second toe. I'm concerned it's spreading. Though I don't know what "it" is.
Any suggestions or advice would be welcome. These are my first chicks. I've already lost one to unknown causes. Really don't want to lose anymore.

 

[f8thnjc]

Is it using the foot that is black? Sounds like the flesh is dying for some reason, or there is restricted blood flow for some reason. Is it acting healthy? Hope someone who has seen this before can chime in.

 

[Lionbee]

Other than the toe being black she seems fine. She uses the foot.