Ok, I come home last night and check on the tank only to find that my Yellow Tang has a red coloration over his body?? I can't find any info on this and I've never had any probs before. Water contents are good, and everything else in the tank is fine...
What are you feeding? Sometimes pigments come through the skin and change the colors. What are your lights like? Is it a severe spectrum shift? Do a water change and call the boards in the morning...
luck
Is it under the skin like a pigment change or does it look like streaks of blood?
The first would most likely be from what is being fed. And the second would be hemoraging under the skin. It sometimes is accompanied by HLLE(head and lateral line disease).