Random new Stretch marks??

So I gained about 17 pounds (I went from 108 to 125) this past year. All of a sudden I look down at my thighs and I have stretch marks all over them. I’m 18, so I’m pretty much done puberty I thought. Can you get new stretch marks from just a 17 pound weight gain? I didn’t even notice a difference in the circumference of my thighs.