A few weeks ago, I noticed that on my bicep/shoulder area, I had these funny looking lines. I learned they were stretch marks, but I'm kinda confused. I'm 17 and male, and was a very late bloomer. I just started having large growth spurts a while back, but didn't have any stretch marks. I started lifting weights, but haven't noticed my muscles growing much. So, if the stretch marks aren't from working out, is it normal to get them just from growing?
Thanks in advance.