Well they were just tested by the state abt. 3 weeks ago so it's not pullorum. They are not acting sick and no signs of cocci.I'd call that comb more purple or even pale than black.
Paratyphoid, spirochetosis, ergotism are possibilities but almost anything that would affect the comb would have other symptoms.
Coccidiosis, lymphoid leucosis and pullorum can cause a pale comb.