Red Marks on Green Chromis

[jords]

Purchased 5 green chromis about 2 months ago. Today, I noticed red marks on one of them. Hours later, he is staying near the top and breathing heavy.
Disease or aggression? Something else?


Parameters are all perfect. Tank is 50 gallons and also has standard clownfish, tube anemone, and torch frag.

Hopefully the photo helps. No signs on other fish. Any help would be great!