My Son Is 16 And Rows, 6'4 168 Lbs Last

My son is 16 and rows, 6'4 168 lbs last year he started rowing and also started having nose bleeds. We chalked it up to a major growth spurt. He's now doing indoor rowing on ergs and nose bleeds 2-3 x a week and coughing/spitting up blood when he rows/ergs 5-6 times a week.
Should we be concerned?