Those are chromis not damsel very close to the same though... How large is your school because when i had a school of the blue/green chromis the adult dominant male would always beat up the next biggest chromis to keep him in check I'm thinking which resulted in similar wounds due to the attacks and the fish rubbing on the rocks due to stress...IMO id never put another chromis or damsel in any of my tanks ever again..the little demon fish haha