Black stuff on barred rock combs?

[Erin80]

3/5 of my rocks have this.....what is it?

 

[RodNTN]

It appears to be some kind of scab.

 

[Eggcessive]

Looks like they have had the combs pecked.

 

[Hen Pen Jem]

If they are scabs from pecking, they will heal up in a week or so. Otherwise, may be fungus.

 

[CapricornFarm]

Might be fowl pox?