Red Comb turning black

[Chap]

My Bared Rock Rooster's comb is turning black at the tips. I live in Texas and its August, so no frost bite. Here's the thing... iv been watching him for a while and his comb will be bright red one day and the tips will turn black the next. His comb was a healthy red yesterday, and now today it looks like this...(see photo).

Also, he has no other visual symptoms, he is a free range roo, with two hens. He crows good and is very active.

 

[Wyandottes7]

It's probably just because of the heat. Cold and hot temperatures will cause the comb to blacken or turn purple slightly. Another possibility is that he has some heart problems.

 

[R.M.Qureshi]

Please observe his droppings for any sign of black head. Have you noticed any abnormal behavior.

Have a look at the link below
http://https://skydrive.live.com/redir?resid=A99F88838D34E678!250&authkey=!AAOQW5GvPFg0J30

Rehan M