Jour

Being young doesn’t really matter as you can also damage your hearing if exposed to loud sounds, but I digress. Regarding channel imbalance. If your amplifier uses old school potentiometers channel balance is certainly a thing. So you indeed need to test that imbalance with other sources. Also I have been enjoying music since my teens and I’m now in my forties, imbalance with headphones was a pretty rare thing for me, as for IEMs besides the rare QC thing I never had that kind of problems. I know it’s a long shot but you should test your amplifier section for DC offset…most amps filter it but one is never too cautious as it can ruin gear.