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That's a symptom of congestive heart failure (CHF). The combs turn dark purple when they're resting on their keels, then when you make them get up and move around, the color will return to red, at least for a while, until the condition progresses more. This is caused by impaired blood circulation. The heart is becoming compressed by the excess fat in the body cavity. This compression is greater while the bird is at rest, with the weight of the body pressing on the heart area. That why when they stand up and walk around, the color returns to normal, the pressure is removed from the keel, and the blood circulates better.
It has nothing to do with cocci, it's because they grow so fast, and get so fat. When a bird starts to show a purple comb, butcher before they drop dead. The meat is safe to eat.
"Flip" is a specific type of death from heart attack, that causes the bird to flip over onto it's back when it dies. Flip can occur from CHF, but the heart can fail in other ways from CHF, minus the flipping over part, and it's basically the same thing. They die of heart failure.