My Son Is 14 And Has Been Having On And

My son is 14 and has been having on and off chest pain and shortness of breath when playing soccer. He has a heart murmur that was diagnosed at 3 then followed up with an echocardiogram where he was cleared of all valve/major issues. He has played competitive travel soccer since he was 7 and only has noticed this issue in the last year. We have eliminated any caffeine at least 24 hours before practice/games, though we did notice less symptoms when caffeine was removed completely. The symptoms are not consistent and only happen randomly. Tonight during practice he complained of pain down both arms, pain in his middle back that spreads, heart racing and shortness of breath. As soon as he sits for a few minutes all symptoms subside. You can still hear his heart murmur listening with a stethoscope, but he has been cleared every year to play soccer. Should I have more test done or could this correlate with the onset of puberty?

Thank you for your help! Stephanie